Chapter updated in October 2023.
- Major update of all sections.
A description of changes can be found at Updates to the Communicable Disease Control Manual.
Cases of wild poliovirus (WPV) have decreased by more than 99% since 1988. Wild strains 2 and 3 were declared eradicated in 2015 and 2019 respectively. At the end of 2022, only Pakistan and Afghanistan have endemic transmission of wild polio virus (WPV) type 1.
However, approximately 36 countries reported polio outbreaks in 2022; these countries are experiencing re-infection either through the importation of wild or vaccine-derived poliovirus from another country, or the emergence and circulation of vaccine-derived poliovirus (cVDPV) in the community.
Cases of circulating vaccine derived poliovirus (cVDPV) (especially type 2) were reported in multiple countries in 2022. The majority of cases were reported in central African countries, however, due to inadequate vaccination rates associated with the COVID-19 pandemic, cases were also reported in the United States, Indonesia, and Israel. In addition, there have been wastewater detections of cVDPV poliovirus in several countries without polio cases, including the United Kingdom and Canada.
Up-to-date information on the current spread of different poliovirus strains around the world can be found on the Polio Global Eradication Initiative website.
New Zealand Epidemiology
Wild poliovirus has been eliminated from New Zealand, with the last case of wild poliovirus infection occurring in New Zealand in 1977. No cases of vaccine-associated paralytic poliomyelitis (VAPP) have occurred in New Zealand since the oral polio vaccine (OPV) was superseded by the inactivated polio vaccine (IPV) and withdrawn from the immunisation schedule in 2002.
Importation of poliovirus remains unlikely but possible, with increasing cVDPV cases globally, including in countries with strong travel links to New Zealand. Low vaccination rates1, especially among young children who are the most susceptible to infection, are of concern, as local spread of the virus could happen in communities with low immunisation rates and result in polio cases.
There were three serotypes of wild poliovirus (WPV) (genus Enterovirus) serotypes 1, 2, and 3 until WPV 2 and 3 were eradicated (Jafari,2015). While most disease is mild or asymptomatic, all serotypes can cause paralysis, though, the proportion of paralytic cases vary from 1/200 for serotype 1 to 1/1000 for serotypes 2 and 3.
There are also three serotypes of vaccine derived polioviruses (VDPVs). These are “revertant” strains which have mutated or recombined from the live attenuated sabin-strain viruses included in the oral polio vaccine. VDPVs have regained neurovirulence and, as with WPVs, can also cause paralysis. Currently, serotypes 2 and 1 account for the majority of cVDPV infections.
Circulating VDPVs pose the same public health threat as wild polioviruses because they have recovered the biological properties of wild polioviruses. Circulating VDPVs have the potential to re-establish endemicity in settings of low (ie, type-specific) polio vaccine coverage, and require the same control measures.
Humans are the only reservoir (Jafari,2015). No long-term carriers of wild-type poliovirus have been detected. Chronic carriage of vaccine-derived poliovirus has been reported, all from high-income countries or emerging economies and all associated with primary B-cell immunodeficiency syndromes. Immunodeficiency- associated VDPVs may be excreted by individuals with primary immunodeficiency (PIDs) for many years with no apparent paralytic signs.
Polioviruses can remain viable in soil, water and sewage for several weeks and have been isolated from floors, furniture, and clothing for at least several days (Jafari,2015). Survival is affected by temperature and humidity with greater survival in lower temperatures and higher humidity (Fine, 1999).
The term ‘poliomyelitis’ only refers to poliovirus infections that result in paralysis, also known as ‘paralytic poliovirus.’ All poliovirus infections that do not result in paralysis are referred to as ‘non-paralytic poliovirus.’
Most poliovirus infections are asymptomatic or involve mild symptoms which resolve over a period of 7-10 days.
It is estimated that mild symptoms occur in 10-25% of infections (CDC, 2021; ECDC, 2021). Symptoms may include fever, headache, sore throat, gastrointestinal disturbances; malaise; neck and back stiffness; and pain in the limbs, back and neck.
Severe symptoms occur in 1-2 percent of infected unvaccinated individuals. Acute flaccid paralysis occurs in 0.5-0.05 percent of infected individuals, and is more common in adults, where the incidence may be as high as 1 in every 75 infections (Immunisation Handbook, 2017). Severe illness often includes aseptic meningitis, which can precede development of paralysis (Simionescu et al., 2023).
Acute flaccid paralysis is characterised by:
- rapid onset of weakness of an individual’s extremities, often including weakness of the muscles of respiration and swallowing, progressing to maximum severity within 1-10 days.
- The term “flaccid” indicates the absence of spasticity or other signs of disordered central nervous system (CNS) motor tracts such as hyperflexia, clonus, or extensor plantar responses.
(Excerpt from Acute onset flaccid paralysis; World Health Organization 1993; WHO/MNH/EPI/93.3. Geneva)
In children who develop paralysis, the illness may be biphasic with the initial phase of one to three days’ duration being indistinguishable from that of other viral infections. The child appears to recover but then two to five days later meningism develops rapidly, followed by paralysis (CDC, 2021).
In adults and adolescents, paralytic poliovirus infection usually presents with a gradual onset of paralysis and pain without the early symptoms. Symptoms usually worsen over 2-3 days but can continue to worsen for up to a week (Simionescu et al., 2023). Cases usually have evidence of meningeal irritation and clinicians need to be vigilant for that as a prodrome to the onset of paralysis.
Polio can be excluded from the diagnosis for adult AFP cases if they also have
- Nerve conduction studies showing demyelinative changes OR
- Cerebrospinal fluid (CSF) albumino-cytologic dissociation.
Polio should be suspected in adult AFP cases where there is CSF pleocytosis.
AFP presentations are more commonly due to other conditions such as Guillain-Barre syndrome (GBS) or transverse myelitis, however, as part of surveillance efforts for the global eradication of polio, infection must be considered and ruled out in all paediatric AFP cases.
For more information visit Healthpathways.
Spread of infection
The incubation period for the onset of paralysis in paralytic poliovirus infection is usually 7 to 21 days, although the reported range is 3 to 35 days (CDC, 2021).
The incubation period for nonparalytic poliovirus infection is reported to be 3 to 6 days (CDC, 2021) but published literature supporting this, or describing when the virus can be detected in asymptomatic cases, is scarce. Evidence from OPV clinical trials suggests the mean time for first testing positive in vaccine recipients was 3-4 days. However, the mean time for testing positive for household contacts of vaccine recipients was 10-17 days (6-13 days after vaccine recipients tested positive) (Altamirano et al, 2018). This may suggest a longer eclipse period when the exposure dose of contacts is lower.
Mode of transmission
Polio is spread through person-to-person contact via the faecal–oral and less commonly via the oro-oral route (Jafari, 2015).
It can be spread:
- directly from person to person through contact with the faeces of an infected person, or when an infected person coughs or sneezes
- through drinking water or eating food contaminated with faeces (eg water contaminated with untreated sewage; or food prepared by a person with poliovirus infection) (NSW Health, 2022).
Poliovirus is highly infectious.2 It is easily spread by individuals with or without symptoms. It is estimated that 90-100% of susceptible household contacts will seroconvert and test positive for polio (CDC,2021).
Cases are likely to be most infectious in the 7 – 10 days before symptoms start until 7-10 days after the onset of any symptoms (ECDC, 2021; Australian Department of Health and Aged Care, 2022). However, transmission is possible for as long as the virus continues to be excreted.
Poliovirus has been detected in throat secretions as early as 36 hours, and in faeces 72 hours, after exposure to infection. Poliovirus typically persists in the pharynx for about one week and in faeces for three to six weeks. However, it may be shed in the faeces of immunocompromised people for several years (NSW, 2022).
Equity considerations and priority populations
Clinical risk of severe disease (paralysis and increased mortality)
For polio, the following groups have been identified as being at higher risk of clinical severe disease or higher public health risk.
Anyone who is not fully vaccinated either with OPV or IPV, particularly those who are unvaccinated and are:
- Adolescents or adults
Pregnant women may also experience severe disease and have a higher risk of miscarriage.
For the management of cases and contacts at risk of clinical severe disease, ensure that their management is discussed with the appropriate clinical team and that a primary healthcare provider follows up regularly with close contacts in isolation. Refer to contact management below for further information.
Public health risk
Groups at higher risk of transmission (to either large numbers of people or at-risk groups) include those who have not been vaccinated or only vaccinated with IPV (not OPV):
- have attended a high-risk setting ie. food premises, early learning service, school, healthcare setting or other setting with large numbers of people in close contact for an extended period of time
- are immunocompromised
- are in high-risk occupations such as food handlers, healthcare workers, ECE teachers, carers.
Priority populations for communicable disease management:
Pae Ora strategies recognise that achieving equitable outcomes for all populations is a priority for the health sector.
The following groups are at risk of inequitable health and wellbeing outcomes due to poorer access to health services and/or the increased impact of public health measures (e.g. economic impact of quarantine):
- Pacific peoples
- Tangata Whaikaha – Disabled people
- Those living rurally
- The unenrolled population
- Those from high-deprivation situations
Other ethnic minority groups*, migrants, refugees, asylum seekers and RSE workers are also identified as priority groups for public health support.
Public Health Services should refer to the actions listed in General considerations for the control of communicable diseases in New Zealand to prepare their service well for meeting the needs of all these groups in preparation, and response to, all communicable disease outbreaks.
* Note, migrants/refugee communities may have countries of origin where polio is endemic or there is circulating VDPV, and therefore may theoretically have a higher risk of exposure to polio. However, despite this risk many of these communities may be well-vaccinated; particularly due to resettlement processes coming to Aotearoa.
Polio-specific equity considerations:
Poliovirus case and contact management involves quarantine and isolation, stool samples** and considerable wait times for test results. Requirements for quarantine and testing are likely to have a disproportionate impact on priority populations when compared to other population groups. Therefore, cases and contacts who identify with one or more of the population groups listed above, should be prioritised for management where possible to mitigate inequitable outcomes.
Priority cases and contacts
To ensure polio cases and contacts have the appropriate support and information, clinicians and public health staff should take time to:
- Undertake whakawhanaungatanga
- Seek to understand what supports and services are most helpful and whether meeting face-to-face or remotely is more helpful
- Ensure there are clear channels for questions to be answered and key messages are understood
- Ensure appropriate cultural and language support is offered
- Ensure appropriate clinical support is in place
Further guidance on stool sampling specifically is provided in the Testing Guidelines section below.
Polio is a vaccine preventable disease.
The inactivated polio vaccine (IPV) is part of the National Immunisation Schedule. IPV superseded the oral polio vaccine (OPV) in 2002 as the preferred vaccine in New Zealand. For more information on the vaccine and recommended immunisation schedule refer to the Immunisation Handbook.
Paralytic poliovirus infection (poliomyelitis)
- A clinically compatible illness characterised by
- acute flaccid paralysis (AFP) of one or more limbs with decreased or absent deep tendon reflexes in affected limbs AND/OR
- a possible effect on bulbo-respiratory muscles (bulbar muscles are those in the mouth and throat which are responsible for speech and swallowing) AND
- no sensory or cognitive loss
Non-paralytic poliovirus infection
- Either an absence of symptoms or any non-paralytic symptoms such as fever, headache, sore throat, gastrointestinal disturbances; malaise; neck and back stiffness; and pain in the limbs, back and neck.
- Recent travel to high-risk countries (wild poliovirus or circulating vaccine derived poliovirus, see the Polio Global Eradication Initiative website for an up-to-date list)
- Exposure to high-risk individuals (a person with polio infection, a person immunised with OPV within the last two months, a person with a history of travel to high-risk countries within the last three months, or a person working with poliovirus in a laboratory)
- Exposure to poliovirus in a laboratory.
- Definitive evidence for a confirmed case requires isolation of poliovirus or detection of poliovirus nucleic acid from a clinical specimen.
- Further detail, including information on acceptable clinical specimens, is provided in the Testing Guidelines section below.
Confirmed: Laboratory confirmed infection with poliovirus where there is:
- Paralytic poliovirus infection: case meets clinical criteria for paralytic poliovirus infection and laboratory criteria for confirmed poliovirus infection OR
- Non-paralytic poliovirus infection: case meets clinical criteria for non-paralytic poliovirus infection and laboratory criteria for confirmed poliovirus infection. This case classification should not be used for individuals who received OPV in the prior 6 weeks if a Sabin-like virus is detected
Probable: case meets clinical criteria for paralytic poliovirus infection but does meet laboratory criteria for confirmed poliovirus infection. The following must also apply:
- experts, such as the National Certification Committee for the Eradication of Polio, or a relevant clinician such as a paediatrician or neurologist, consider polio cannot be excluded as the cause of the person’s illness
- No other diagnosis has been confirmed AND
- the individual meets the epidemiological criteria.
Under investigation: A case that has been notified as a suspected case of poliovirus infection3, but information is not yet available to classify it into any of the other categories.
Not a case: A case that has been investigated and subsequently found not to meet the case definition, including cases under the age of 15 years who have been deemed to have a non-polio paralytic illness by the National Certification Committee for the Eradication of Polio.
Confirmed cases can be further classified depending on the genomic profile of the detected virus. ESR will advise on subclassification of any viruses detected. Further information is available at The Virus – GPEI (polioeradication.org).
- Vaccine-associated paralytic poliomyelitis (VAPP): Isolation or detection of Sabin-like poliovirus (OPV strain) in an individual with paralysis. This is a very rare event (2-4 cases per million doses) which occurs when the live attenuated virus in OPV has genetically reverted in the intestine of a susceptible individual to become neurovirulent. (Polio Global Eradication Initiative, nd).
- Sabin-like poliovirus infection: Isolation or detection of Sabin-like poliovirus (OPV vaccine strains) in an individual without paralysis. This classification should not be used if the individual has been vaccinated with an oral polio vaccine in the six weeks prior to the date of specimen collection (or longer if the individual is immunocompromised4). OPV is now bivalent with only serotype 1 and 3 contained in the vaccine
- Wild virus-associated poliovirus infection (WPV): Isolation or detection of wild poliovirus. Historically there were three serotypes of WPV -type 1, type 2 and type 3. Only type 1 WPV remains in circulation. Type 2 WPV was declared eradicated in 2015 and type 3 WPV was declared eradicated in 2019 (PGEI, nd).
- Vaccine derived poliovirus infection (VDPV): Isolation or detection of OPV virus strains that are sufficiently divergent to meet WHO criteria for a vaccine derived poliovirus. For types 1 and 3 this is >1% divergent, and for type 2 this is >0.6% divergent (PHE, 2019). VDPVs emerge when the virus in OPV circulates in under-immunised populations for long enough (12-18 months) that revertant or recombinant mutations occur which cause it to become neurovirulent (capable of causing paralysis).
- VDPV’s can be further categorised as circulating VDPV (cVDPV), immune deficiency associated VDPV (iVDPV) and ambiguous VDPV (aVDPV). For more information on these categories please refer to National Response Framework.
Laboratory confirmation of poliovirus infection requires isolation of poliovirus or detection of poliovirus nucleic acid from a clinical specimen.
Samples for Collection
The following clinical specimens should be collected for detecting the presence of polioviruses or related antibodies. (Note: Not all samples need to be taken – stool samples are required for laboratory confirmation– however, other samples can be tested)
Appropriate timing of specimen collection:
Nature of specimen
Two fresh stool samples (or rectal swab with faecal material if stool is not immediately available) collected 24 hours apart.
Preferably within 14 days of paralysis onset but can be collected up to the 4th week of illness.
Additionally, the following samples can be tested:
Swab in universal transport (UTM)
Taken first week of illness
Cerebrospinal fluid (CSF)
Early in the illness
If enterovirus was detected as part of clinical work up
First week and 2-3 weeks later (and convalescent sera).
Serology can be useful in specific circumstances. See below for further information.
Isolation or detection of polio in any of these samples is sufficient to confirm a diagnosis of polio. To exclude polio:
- for the purposes of case management, a negative stool sample is required, and
- for WHO surveillance purposes, two negative stool samples that have undergone culturing are required.
Collecting Stool Samples
Stool samples should be sent to ESR via the local laboratory, labelled ‘for AFP surveillance’.
A rectal swab with faecal material may be provided if it is clinically impossible to obtain a stool sample within the timeframe - a discussion with a clinical microbiologist is recommended in this instance.
Standard and Contact/Enteric precautions are required for stool sample collection. Ensure all collection containers are pre-labelled. Refer to IPC section for further details.
Collecting stool samples can be a confronting experience. Maintaining cultural safety is paramount. To do this:
- Meeting kanohi ki te kanohi (face to face) with the person being tested in appropriate personal protective equipment (PPE) where possible is often preferred – ensure the approach taken is specific to the case or whānau at hand.
- Plan for the visit to be prepared with information, case - contact management process and any questions they might have
- Ensure language barriers will not be an issue with the use of multilingual staff and/or translation services where needed.
- Adapt how the process is discussed for the person/whānau in question, including ensuring there are whānau members or other support people present where needed.
- Discuss the specimen collection after a case or contact interview and any questions about any manaaki (support) they may need to quarantine or isolate safely).
- Ensure it is clear to the person being tested that stool sampling is the best way to test for polio.
- In most instances, the collection of the sample at home is preferable (not applicable if sample provider is hospitalised). Provide a sampling kit with verbal instruction on how to use the kit.
- Where sample collection is done at home, consideration should be given to getting the sample from the home to the lab, including arranging for home pick-up where this is preferred by the person providing the sample.
- Ensure any questions the individual or whānau have about sample collection are answered.
- Engagement with community and/or religious leaders of affected groups is essential in an outbreak.
- Local variation may apply.
The WHO considers viral culture to be more sensitive than pan-enterovirus or pan-poliovirus PCR directly from stool specimens and it is currently the gold standard for polio diagnosis. Improved stool extraction protocols to increase the sensitivity of NAATs may make it as sensitive as virus culture and further sensitivity validations are currently being performed. It is therefore still the method which should be used for confirmation of acute flaccid paralysis and therefore 2 stool samples collected 24 hours apart within 14 days of illness onset should always be sent to ESR when a case is investigated for polio. However, the turnaround time for viral culture is 14 days and therefore pan enterovirus and/or pan poliovirus PCR testing, may be considered to preliminarily diagnose enterovirus or exclude poliovirus infection for public health management purposes.
- Pan Enterovirus (EV) PCR testing
Pan EV PCR testing should be performed on all samples collected as part of the clinical or public health management either at the local hospital laboratory or their referring specialist laboratory to speed up diagnosis. It is important to note that local laboratories must be confident that their assay will pick up enteroviruses (serving as the initial screening assay for polioviruses).
For urgent suspected poliovirus infection samples, the turn-around time for an EV PCR result is typically 24-48 hours in regional labs depending on where the sample is referred from and to.
A negative pan EV PCR (from appropriate stool specimens) makes poliovirus infection unlikely. For public health purposes, negative results from pan EV PCRs can be used to determine the management pathway for suspected cases or close contacts (for example, an AFP case with a negative pan EV PCR can be treated as ‘not a case’). However, to ensure exclusion of polio and to meet surveillance requirements, for suspected cases a second stool sample needs to be collected and both need to be sent to ESR for poliovirus culture.
A positive pan-enterovirus PCR result does not confirm poliovirus and further testing will be required to specifically detect poliovirus. All PCR enterovirus samples should be sent to ESR’s Virology Laboratory in Wallaceville, which is the reference laboratory for genotyping and confirmation. Priority should be given to PanEV positive CSF and stool samples from patients who fulfil the poliovirus clinical case definition or those who present with meningoencephalitis.
- Intratypic Differentiation PCR
ITD RT-PCR (Intratypic Differentiation) and VP1-based enterovirus sequence typing can be performed on enterovirus PCR positive samples in suspected polio cases or close contacts to reduce the turnaround time and provide a further indicator of positivity. This will facilitate rapid contact tracing prior to laboratory definitive evidence of poliovirus infection from stool culture.
ITD RT-PCR can also further distinguish the strain of poliovirus (wild or vaccine derived). Isolation by culture and subsequent typing can take up to 28 days.
All EV PCR positive samples referred for typing and surveillance will undergo sequencing with a 1.5-week turnaround time.
Poliovirus serology testing (i.e. anti-poliovirus neutralization assay) does not differentiate between acquired, vaccine induced or passive antibodies (frequent given Immunoglobulin therapy). However, serology may be useful in further investigating a probable case when a diagnosis cannot be established by molecular or culture-based methods, by comparing titres in acute and convalescent sera providing no Immunoglobulin therapy or recent blood transfusion was given. Serology assays can also be used in assessing poliovirus antibody prevalence in a population.
Where poliomyelitis serology is used, collect an acute serum specimen as early in the course of disease as possible and a convalescent specimen at least three weeks later. Ensure molecular or culture-based testing methods have been attempted.
Antibody tests for polio infection are available at ESR (minimum volume required is 300 uL serum) after discussion with a clinical microbiologist/virologist. Both acute and convalescent sera should be referred together by the local testing laboratory.
A direct laboratory notification flowchart is available in the CD Manual Appendix.
Notification and Escalation Procedures
Local and National Notification
Clinicians must notify the local Medical Officer of Health of all suspected cases of polio. In adults, this would include but may not be limited to all AFP cases aged >15 years that:
- meet epidemiological criteria and
- CSF studies and nerve conduction studies have not identified an alternative diagnosis.
Clinicians should not wait until test results are available. Public health services should ensure appropriate testing has been undertaken. As viral shedding can be intermittent, two stool samples collected (at least 24 hours apart) should be sent to ESR (see lab testing).
See below for notification of paediatric AFP cases.
National reporting of paediatric AFP cases to the New Zealand Paediatric Surveillance Unit
As part of New Zealand’s commitment to global polio eradication, polio must be excluded in all children (aged <15 years) who present with AFP. This requires clinicians to report all paediatric AFP cases to the New Zealand Paediatric Surveillance Unit (NZPSU) at the Department of Women’s and Children’s Health, University of Otago, Dunedin. For many of these cases, there may not be a high index of suspicion* for polio.
Contact the New Zealand Paediatric Surveillance Unit
Phone: 021 278 1728
All cases must have a full clinical and epidemiological assessment and virological investigation of stool specimens. Two stool samples collected 24 hours apart within 14 days of onset of paralysis must be collected to exclude polio as a diagnosis. These should be sent to ESR via the local laboratory, labelled ‘for AFP surveillance’. A rectal swab with faecal material may be provided if it is clinically impossible to obtain a stool sample within the timeframe.
All cases are discussed by the National Certification Committee for the Eradication of Polio, and records of its deliberations are reported to the WHO. The NZPSU provides Manatū Hauora/Te Whatu Ora with regular summaries of all paediatric AFP cases referred to their service where polio has been excluded. The NZPSU will inform Manatū Hauora/Te Whatu Ora urgently of any paediatric AFP where there is a high index of suspicion for polio.
For more detailed information on AFP surveillance, see the NZPSU website.
The Medical Officer of Health must inform Manatū Hauora/Te Whatu Ora of all confirmed cases of polio and suspected cases where there is a high index of suspicion* for polio. The NZPSU will ensure notification of paediatric AFP cases where there is a high index of suspicion (see below). Notification should occur as soon as possible and within 24 hours of detection by phone 0800 GETMOH or email firstname.lastname@example.org .
*High index of suspicion criteria will vary depending on the current national and international context. Criteria may include: an epidemiological link to a case, recent travel to a country with polio cases or wastewater detections, residence in an area of New Zealand where polio has been detected in wastewater.
WHO declared the international spread of polio a Public Health Emergency of International Concern (PHEIC) under the International Health Regulations (IHR 2005) in 2014. WHO issued Temporary Recommendations and requested a reassessment of this situation by the Emergency Committee every three months. This process is still on-going.
Under the WHO’s International Health Regulations 2005 (IHR), assessment of any suspected case of paralytic poliovirus infection must occur within 48 hours of initial identification. The WHO requires notification within 24 hours of any human or wastewater detection of polioviruses (other than Sabin/sabin-like type 1 or 3 viruses) and any exposures due to containment breaches in a laboratory.
The Ministry of Health National Focal Point is responsible for notifying the WHO within the required timeframes. Additionally, ESR, as the WHO-accredited National Poliovirus Reference Laboratory, will send confirmation of any positive results to the WHO. See Polio Response Framework.
Management of contacts
Poliovirus is excreted in faeces and oropharyngeal secretions of cases and can remain viable for days or weeks on surfaces, fabrics, in soil, food and in water. Contacts exposed to faeces, oropharyngeal secretions or potentially contaminated food/water/objects/surfaces may be at risk of being infected with polio.
Contact tracing should focus on the 7-10 days prior to development of symptoms, or positive test result, up until the time the case was identified or is considered not to be infectious.
Because poliovirus serology testing does not differentiate between acquired or vaccine induced antibodies, serology cannot be used to identify susceptible close contacts or to inform management of close contacts ie to identify contacts who will not be required to quarantine.
Impact of vaccination on contact management
Both IPV and OPV provide high levels of protection from severe disease and paralysis. However, only OPV provides high levels of protection from infection with polioviruses. This means individuals fully vaccinated with IPV can become infected and effectively transmit the virus to others
For this reason, the management of close contacts may differ according to whether a contact is fully vaccinated and whether they received OPV as part of their vaccination regimen.
IPV acts by inducing serum antibodies to poliovirus but does not induce sufficient mucosal immunity to prevent infection and excretion of polioviruses in the gastrointestinal tract. Protection from severe disease is expected to be lifelong. IPV efficacy against paralytic polio is 90% after 2 doses and 99%-100% after 3 doses.
OPV induces high levels of intestinal mucosal immunity, which makes it highly effective at preventing infection and excretion of polioviruses in the gastrointestinal tract. A single dose of OPV (if it covers the circulating virus type) when combined with IPV is sufficient to provide protection from infection to the poliovirus strains included in the vaccine. Protection is expected to be lifelong – however, as antibody levels show some reduction over time, booster vaccination with IPV can be used to maintain immunity.7
Since 2002, IPV alone or in combination with other antigens has been the only polio vaccine used in New Zealand. Prior to 2002, both vaccines were available, although OPV was gradually phased out in the 1980s and 1990s. If evidence of specific vaccine type is not received, contacts should be managed as if they had only received IPV.
OPV continues to be used in vaccination programmes internationally. Since 2016, a bivalent vaccine containing type 1 and type 3 strains has been used globally, replacing the trivalent oral poliovirus vaccine. This means most individuals vaccinated with OPV since 2016 will not be protected from cVDPV type 2 infection or transmission.
Contacts can be grouped into two categories: close contacts, and casual contacts. The following provides guidance on how to categorise contacts. The local Medical Officer of Health or their delegate(s) may use their discretion in deciding the most appropriate contact category.
A close contact is anyone with any of the following exposures during a case’s infectious period:
- Direct contact with the faeces of a case (or materials potentially contaminated with faecal matter from a case8). This includes anyone who
- changed the nappy of a case
- washed soiled clothes of the case
- frequently shared the same toilet as the case without cleaning between users,
- had contact with sewerage (septic tanks may pose a particular risk) from a case
- Direct physical contact with a case (including contact with oropharyngeal secretions in the early stage of the case’s illness). This includes:
- kissing or other intimate physical contact
- contact with droplets from coughs and sneezes
- sharing of utensils, toothbrushes, drinks from the same glass, cigarettes, or vapes where oropharyngeal secretions could be exchanged
- healthcare workers caring for a case without sufficient PPE and adequate IPC precautions9
- disability and other personal support workers who shower, dress, toilet, or otherwise attend to the personal needs of the case without sufficient PPE and adequate IPC actions.
- Prolonged (>4 hours cumulative) contact in an indoor setting (eg house/car). This includes:
- household contacts or overnight visitors
- children and staff in the same early childhood education, day-care environment or the same classroom at a school,
- social contacts or work contacts who spent more than 4 hours with the case on one occasion, or for periods less than 4 hours on multiple occasions.
- flight contacts who were seated in the same row as the case or who are known to have used the same toilet.
- consumed food prepared by the case
- handled specimens in a lab without sufficient IPC precautions.
A casual contact is anyone who may have had contact with the case during their infectious period, but either the level of contact is unknown, or it is considered unlikely that the exposure was sufficient for infection to occur. This could include any of the following:
- occasional sharing of a toilet with a high level of confidence in diligent hand hygiene
- passengers on a flight where it is unknown if they have shared the same toilet as the case
- healthcare workers exposed to the case with sufficient IPC
- social contacts who have spent less than 4 hours in total with the case during the infectious period, especially if there was only one exposure during this period.
Quarantine and Restriction
Close contacts who meet the following criteria:
- Fully vaccinated with IPV only
- Incomplete vaccination history
- Unknown vaccination history
- History of OPV vaccination which does not include the strain the case is infected with (eg a bivalent or monovalent OPV)
- Household contacts regardless of vaccination history
- five weeks have passed since first exposure to the case; OR
- the contact has had two negative stool samples for polio taken at least 24 hours apart and following:
- 7 days since last exposure to the case during their infectious period, for those whose contact has ended.
- 7 days since the case was released from isolation (or reached day 10 of their infectious period), for those with ongoing exposure to the case.
In addition to the tests-to-release above, consider immediate testing of close contacts to enable identification of individuals who are already cases and/or who could be the source of the case’s infection. This will facilitate early access to appropriate clinical care and enable additional contact tracing to be initiated.
Additional restrictions after release from quarantine
Additional restrictions may be required for close contacts working in or attending high-risk settings such as ECEs, schools, healthcare settings, and food premises. This could include the following:
- restrictions from attendance until an additional two negative stool samples 7 days after release from quarantine
- strict compliance with IPC requirements.
Close contact fully vaccinated with a schedule that includes at least one dose of OPV*
*The OPV dose must include the detected virus strain and documentation is required to prove vaccination.
Quarantine is not required. However, to minimise the risk of transmission, restriction from attendance at high-risk settings such as healthcare, schools, ECEs and food premises are recommended.
- Restrictions are recommended until two negative stool samples at least 24 hours apart have been received. Testing should not commence until at least 7 days after the last exposure to the case.
- If stool samples cannot be obtained for testing, the period of restriction should extend to 5 weeks (the full incubation period for polio).
Casual contacts are not required to quarantine and do not need to be restricted from attendance at high-risk settings.
Monitoring of contacts
Public Health Services should regularly monitor close contacts until they have completed their period of quarantine or restriction. Contacts should be monitored for development of symptoms, compliance with any restrictions or quarantine requirements and to provide information and support as required. Public Health Services should also ensure close contacts’ primary care providers are informed.
Management of symptomatic contacts
If a contact suffers from an illness with neck, back or leg stiffness, severe muscle pain or neurological symptoms, they should seek medical advice. The medical practitioner is advised to:
- refer the patient to hospital as a suspected case of polio
- notify the local Medical Officer of Health of a suspected case of polio.
If a contact suffers from a minor non-specific illness (eg, fever, malaise, headache, nausea, or vomiting) or an influenza-like illness, the medical practitioner is advised to:
- test the contact for poliovirus
- reinforce messages about hand hygiene and disinfection practices
- emphasise the importance of seeking medical attention if symptoms worsen or neurological symptoms occur
- notify the local Medical Officer of Health of a possible case of polio.
Post-exposure vaccination does not prevent infection in contacts; therefore, vaccination will not alter requirements for quarantine or other restrictions.
Vaccination of contacts is strongly recommended, even if the contact is already infected at the point of vaccination. This is because infection with one strain of polio will not protect from infection with other polio strains.
Refer to the immunisation handbook for more information on IPV including contraindications.
Offer a booster dose of IPV to all contacts (including those who received OPV) who have a verified record of the full 3 dose polio vaccination. The three doses can be any combination of OPV (last used in NZ in 2002) and IPV given at least four weeks apart.
A full primary course of IPV should be offered to any close contacts where they are unvaccinated, incompletely vaccinated or have an unknown vaccination history. After the initial post exposure vaccination, subsequent doses for children and young people should be aligned to the National Immunisation Schedule where possible (as long as doses are given at least 4 weeks apart). For those who require catch up, 3 doses of IPV containing vaccine should be offered at least 8 weeks apart (this can be reduced to 4 weeks apart if there is clinical imperative).
Any casual contacts who are either unvaccinated, incompletely vaccinated or have an unknown vaccination history should be encouraged to get vaccinated. Boosters can be offered to those who are vaccinated however, if vaccine supply is limited, priority should be given to those who have not received any vaccine.
Education and support
The local public health unit should advise close contact’s primary care practitioner of their close contact status.
All engagement with contacts and their whānau should be culturally safe and include a manaaki-first approach, considering first and foremost the needs and circumstances of the contact and their household. Contacts should be advised of available supports for quarantine if this is required and public health should seek to understand any other pressing concerns that may inhibit the case’s wellbeing or ability to isolate safely.
All contacts should be provided with culturally safe and accessible information about polio including how it is transmitted and potential consequences, including the rare possibility that paralysis could occur. Translators should be engaged where required, as well as provision of resources in different formats such as Easy read and Braille where available. Close contacts should be advised that they will be followed up regularly by public health to check on their wellbeing, to ensure appropriate testing and provide support for compliance with quarantine and/or any other restrictions.
While being managed by public health, all contacts and asymptomatic cases should be advised to avoid strenuous physical activity, and not undergo a tonsillectomy (as any of these might increase their risk of paralysis).
Contacts should be advised to seek early medical attention if symptoms develop and take precautions so as not to infect others. It is important they telephone and alert the health provider before attending their medical centre to prevent the risk of spreading the virus in health care settings. Contacts should be provided with appropriate mental health support if required in view of the potentially severe consequences of polio.
Management of case
Management may differ depending on the type of poliovirus detected and the characteristics of the case. For example, if the case is classified as VAPP, or is a recent recipient of OPV returning a positive test result, further case investigation, case restriction and contact tracing is highly unlikely to be required.
For immunocompromised cases, case management, including decisions about release from isolation will require a multidisciplinary team approach which includes the Medical Officer of Health and relevant clinical teams.
All cases where poliovirus infection is suspected should undergo case investigation as soon as practicable.
The purpose of case investigation is to confirm the diagnosis, identify contacts at risk of infection, determine the likely source of infection and provide information and support to the case and their whānau. Case investigation should also identify cases at risk of severe disease (eg adults) or prolonged viral replication (eg immunocompromised cases) and ensure referral to the appropriate clinical team if required, as well as cases and their whānau that may be at increased risks of other impacts of disease and/or management on other aspects of wellbeing including economic impacts, ensuring that they have been referred to appropriate wrap-around/social support services.
It is important to take a manaaki-first approach, considering first and foremost the needs and circumstances of the case and their whānau.
Key information to gather is listed below.
- Clinical course of illness and test results (including virus type).
- Polio vaccination history – including recent vaccination with OPV.
- High risk occupations for transmission e.g. HCW, ECE worker, food handler.
- Details of any contacts during the case’s infectious period. Contact tracing should focus on the 7-10 days before and after symptom onset or positive test result and continue until case considered not to be infectious.
- Identification of exposure events. High risk exposure events and/or settings, such as ECEs, health care facilities, shared accommodation facilities, should be prioritised.
- Source investigation should focus on the 30 days prior to diagnosis. Cases should be asked about:
- Known contact with a confirmed or suspected case
- Recent travel or close contact with someone who has a history of recent travel, to areas with poliovirus in circulation, see the Polio Global Eradication Initiative website for up-to-date information on global spread
- Recent travel, or close contact with someone who has travelled, to an area where OPV is being used
- Recent contact with someone who has recently been vaccinated with OPV,
Isolation and Restriction
All suspected polio cases should be advised to isolate until test results are available and a diagnosis of polio is excluded.
Paralytic polio cases will require admission to hospital. Cases should be placed in strict isolation with appropriate IPC measures (see below) to prevent onward transmission.
For asymptomatic/mild cases who do not require hospitalisation, strict isolation at home is required to prevent transmission. Support for isolation should be provided as necessary. Where possible, contact with others in the household, particularly those who are not fully vaccinated, should be minimised until two weeks after symptom onset. This will enable any uninfected household members to have received appropriate vaccination (see contact management for details). Appropriate IPC measures should also be used to minimise the risk of transmission to uninfected household members.
Release from isolation
Cases should remain in isolation (either in hospital or at home) until they are no longer infectious. Immunocompetent cases can be released from isolation when either:
- six weeks have passed since the onset of their symptoms or positive test result; OR
- two consecutive stool specimens taken at least seven days apart are negative for poliovirus.
An individual risk assessment, involving the Medical Officer of Health and relevant clinicians, may be required to determine appropriate release from isolation for immunocompromised cases. If a case continues to excrete virus in their stool beyond six weeks, ongoing restrictions may be required.
There is no cure for paralytic polio and no specific treatments available to alter the clinical course of the disease. Supportive care should be given to address symptoms. Symptomatic cases, particularly those experiencing paralysis, should be under the care of the appropriate clinical team – for example, paediatrics, infectious diseases and/or neurology teams.
Cases with mild symptoms can generally be managed at home, clinicians may want to take a more cautious approach with paediatric cases. As cases who are initially asymptomatic or have mild symptoms may go on to develop more severe symptoms (including paralysis), cases must be provided with information on how to access appropriate clinical care.
Patients should call for help immediately if they:
- are not able to move part, or all, of their body – the body part may also feel stiff, floppy or numb
- are having difficulty breathing or are breathless (NHS website).
Public Health Services must ensure the case’s GP or other relevant clinician is aware and will proactively check-in on patients to monitor their recovery.
For partially immunised or previously unimmunised individuals, a primary immunisation course consists of three doses of IPV-containing vaccine (funded). The recommended interval is at least eight weeks between doses of IPV containing vaccine (funded). This can be reduced to 4 weeks between doses if there is a clinical imperative.
Infection with poliovirus does not confer immunity to other strains of the virus6, so vaccination of the case with IPV is strongly recommended following the acute period of illness and/or infection.
IPV can be given to the case on discharge from hospital or as soon as symptom free.
- If immunocompromised or not fully vaccinated, offer three vaccinations at least 8 weeks apart, or
- follow revaccination schedule as per the immunisation handbook.
- Or, for fully vaccinated cases, offer a booster.
IPV‑containing vaccines are contraindicated if there is a history of an anaphylactic reaction to a previous dose or to any of the vaccine components.
Refer to the immunisation handbook for further information on the vaccine.
Health education and support
Care should be taken to ensure case investigation focusses on cultural safely and sensitivity and includes a manaaki-first approach. Cases should be advised of available supports for isolation and clinicians should seek to understand any other pressing concerns that may inhibit the case’s wellbeing or ability to isolate safely.
Cases and their whānau should be provided with appropriate information about polio, including how it is spread, how to prevent others being infected, and the expected clinical course and prognosis. Translators should be engaged where required.
Public Health Services should ensure asymptomatic/non-paralytic cases are referred to the appropriate clinical team and their primary care practitioner is informed they are a case. Cases should be informed of the potential for symptoms to develop (including rarely paralysis). Teams should be cognisant of the potential mental health impacts of knowing you are infected with a virus that could cause paralysis. Mental health support should be provided.
See section below on IPC requirements for cases.
Special setting management
Special setting management
Public Health services should identify all high-risk exposure events attended by the case. This will include settings where there is a high risk of transmission and/or where there is attendance by those at higher risk of severe disease – particularly individuals who are immunosuppressed. High risk settings include, but are not restricted to, the following:
- healthcare settings
- food premises where the case prepared food for others.
Public Health Services should complete a risk assessment to inform their management. Management will likely include advice on cleaning and PPE, identification and management of contacts, communications to contacts and/or the wider community and a vaccination response.
Other control measures
Infection prevention and control measures
Standard and Contact/Enteric precautions are required by healthcare staff when providing care for a person with suspected or confirmed poliovirus infection. Droplet precautions are additionally required if there are pharyngeal symptoms. These precautions should continue during a person’s hospital stay.
At home, a high standard of hygiene must be maintained until the case is no longer infectious (see section above).
The polio virus can survive at room temperature for a few weeks, live in an infected person's throat or intestines for many weeks and is commonly spread through the faecal oral route.
Hand hygiene is the single most important means of preventing the spread of infection. After going to the toilet, all cases should wash their hands well with soap and warm water for 20 seconds and then dry them thoroughly. Alcohol based hand sanitisers are not as effective as physically washing and drying hands.
If possible, a dedicated separate toilet should be used by cases, if not available, cases or their carers should clean and disinfect the toilet including the flush button/handle every time it is used.
People who have been identified as a close contact of someone who has been confirmed as having polio should adhere to the same advice as described for cases for hand hygiene, cleaning and disinfecting the toilet.
Cleaning and disinfection – Healthcare and general household
Healthcare Note: Products used in healthcare settings should be effective against poliovirus, suitable for the surface or equipment it will be used on and have been approved for use.
Common diluted household bleach solution (0.5%) containing sodium hypochlorite is effective at killing the polio virus. Other disinfectants such as 70% ethanol, isopropanol, and Dettol ®are not suitable for use.
Strength of bleach
Quantity of bleach m/l
Quantity of cold water m/l
Total volume of diluted solution
- To increase the amount of solution made, double (or triple) the amount of bleach and water added.
- A new solution should be prepared daily and kept protected from sunlight.
- Keep all cleaning solutions and products out of reach of children and other vulnerable people.
- When using bleach-based products, it is important that gloves and other personal protective equipment is used to prevent skin and eye irritation.
- Ensure surfaces are cleaned with a detergent and water solution to remove any gross soiling. Failure to do so will reduce effectiveness of disinfection process.
- Ensure surfaces to be disinfected are saturated and leave bleach solution on as long as possible (recommended to leave on surface for at least 5-10 mins contact time) to ensure efficacy. Caution if others using toilet, ensure that surface is dry to prevent skin irritation to others. Bleach solution may be removed after recommended contact time with clean cloth and water.
Linen and laundry
Items that are faecal soiled ideally should be washed at a high temperature (above 60°C) and chlorine bleach additionally added into the wash as per manufacturer’s instructions (if fabric is bleach tolerant). When fabrics cannot tolerate a high temperature, it is recommended that clothes are washed on the highest temperature, they can withstand on a normal wash cycle (not an eco- cycle) using normal amount of washing detergent. If clothing can be tumble-dried, dry through this method otherwise line dry.
Where a case or contact usually uses off-site laundry facilities, public health services should make a plan with the affected household to ensure clean linen and laundry can be obtained safely during their quarantine or isolation period.
It is not recommended for cases to prepare food for others in the household until they are no longer infectious. Any surface used by a case should be cleaned and disinfected.
Utensils and crockery
Ensure that all utensils and crockery are washed thoroughly either with hot soapy water or in a dishwasher. There is no need to keep items separate, but do not share items whilst eating and drinking.
Non-healthcare settings that have been visited while the person was infectious should be cleaned (using detergent and water) and disinfected using diluted household bleach as described under Cleaning and disinfection section.
Special care should be given to bathrooms, change tables and items that may have come into contact with faecal matter or oral secretions.
When using bleach-based products, it is important that gloves and other personal protective equipment are used to prevent skin and eye irritation.
New Zealand uses the WHO’s definition of a polio outbreak, as below.
Detection of WPV or cVDPV with community level transmission as demonstrated by:
- detection in a human, UNLESS there is a travel history to an infected area with 35 days before onset of paralysis OR a confirmed type specific virus exposure in a laboratory or vaccine production facility;
- two separate detections from the environment, where separate means the samples were collected from two different sites with no overlapping catchment areas OR from the same site but at least two months apart;
- any newly detected cVDPV, whether in a human or environmental sample; i.e. when a VDPV isolated either in human stool or the environment can immediately be genetically linked to another VDPV thereby confirming circulation in the areas of detection.
Due to the high proportion of asymptomatic infections, a single case of polio acquired in New Zealand means widespread community transmission is very likely.
Poliovirus infection poses a serious risk to public health and a single case or a single detection in wastewater, requires an urgent national public health response.
Response activities should ensure high levels of vaccine coverage for a resilient population and be guided by a risk assessment which takes into account:
- the vaccine strain identified
- the immunity profile of the community
- population groups at higher risk of infection, transmission and/or severe disease
- population groups at risk of inequitable health and wellbeing outcomes
- environmental risks that could increase risk of transmission (eg flooding, sewerage leaks).
Initial containment measures should focus on effective case and contact management, appropriate cleaning/IPC and management of any environmental contamination. Investigation will be required to determine the extent of spread and should include increased clinical and environmental surveillance. Public communication and rapid implementation of vaccination programmes will be key response activities.
Response activities should include engagement with community and/or religious leaders of affected groups where appropriate.
National operational response plans are developed by the National Public Health Service.
- Altamirano J, Purington N, Behl R, Sarnquist C, Holubar M, García-García L, et al. 2018. Characterization of Household and Community Shedding and Transmission of Oral Polio Vaccine in Mexican Communities With Varying Vaccination Coverage. Clinical Infectious Diseases. 2018;67(suppl_1):S4-s17.
- Altamirano J, Sarnquist C, Behl R, García-García L, Ferreyra-Reyes L, Leary S, et al. 2018. OPV Vaccination and Shedding Patterns in Mexican and US Children. Clinical Infectious Diseases. 2018;67(suppl_1):S85-S9.
- Australian Department of Health and Aged Care. 2022. The Immunisation Handbook: Poliomyelitis. URL: https://immunisationhandbook.health.gov.au/contents/vaccine-preventable-diseases/poliomyelitis
- Brickley EB, Connor RI, Wieland-Alter WF, Collett MS, Hartford M, Van Der Avoort H, et al. 2019. Intestinal antibody responses to a live oral poliovirus vaccine challenge among adults previously immunized with inactivated polio vaccine in Sweden. BMJ Global Health. 2019;4(4):e001613.
- Buonagurio DA, Coleman JW, Patibandla SA, Prabhakar BS, Tatem JM. 1999. Direct detection of Sabin poliovirus vaccine strains in stool specimens of first-dose vaccinees by a sensitive reverse transcription-PCR method. J Clin Microbiol. 1999;37(2):283-9.
- Centers for Disease Control and Prevention. 2021. The Pink Book: Poliomyelitis. URL: https://www.cdc.gov/vaccines/pubs/pinkbook/polio.html
- Ministry of Health. 2017. Immunisation Handbook 2017. Wellington: Ministry of Health. URL: www.health.govt.nz/publication/immunisation-handbook-2017
- Ministry of Health. 2014. National Poliomyelitis Response Plan for New Zealand: Updated 2014. Wellington: Ministry of Health. URL: www.health.govt.nz/publication/national-poliomyelitis-response-plan-new-zealand
- Ooi MH, Wong SC, Lewthwaite P, Cardosa MJ, Solomon T. 2010. Clinical features, diagnosis, and management of enterovirus 71. The Lancet Neurology. 2010;9(11):1097-105.
- Polio Global Eradication Initiative. nd. The Vaccines: OPV. URL: https://polioeradication.org/polio-today/polio-prevention/the-vaccines/opv/
- Simionescu L, Modlin JF, 2023. Poliomyelitis and post-polio syndrome URL: https://www.uptodate.com/contents/poliomyelitis-and-post-polio-syndrome
- World Health Organisation. 2023. Poliomyelitis (polio). Geneva: World Health Organisation. URL: https://www.who.int/health-topics/poliomyelitis#tab=tab_1