Chapter reviewed and updated in December 2017. A description of changes can be found at Updates to the Communicable Disease Control Manual.
New Zealand epidemiology
Episodes and outbreaks of acute gastroenteritis are common in New Zealand. They are usually due to microorganisms. Outbreaks of poisoning due to a chemical contaminant of water or food have only rarely been reported.
More detailed epidemiological information is available on the Institute of Environmental Science and Research (ESR) surveillance website.
Further information on foodborne illness is available on the Ministry for Primary Industries website.
Acute gastroenteritis is a descriptive term for inflammation of the gastrointestinal tract from any cause. It commonly presents as the sudden onset of diarrhoea and/or vomiting. Diarrhoea is defined as more frequent (>= 3 per day) and loose stools three or more times per day. These symptoms can be present in many medical conditions, especially in children. Symptoms may be toxin-mediated and other than gastrointestinal. Acute gastroenteritis can be caused by ingestion of:
- toxins, for example, toxins produced by Bacillus cereus, Staphylococcus aureus, Clostridium botulinum, tutu plant (Coriaria)
- viruses, for example, norovirus, rotavirus
- bacteria, for example, Campylobacter spp., Salmonella spp., Yersinia spp, E. coli
- parasites, for example, Giardia, Cryptosporidium
- chemicals, for example, some metals.
Acute gastroenteritis is not necessarily notifiable, unless:
- there is a suspected common source
- it is in a person in a high-risk category (food handler, early childhood service worker, other person at increased risk of spreading it)
- it is an infectious gastroenteritis of public health importance.
Notification is required for single cases of chemical, or toxic food poisoning such as botulism, histamine (scromboid) poisoning and, toxic shellfish poisoning (any type).
In addition to acute gastroenteritis, there are also specific notifiable enteric diseases covered in other chapters; these are Shiga toxin-producing Escherichia coli (STEC, previously known as VTEC), Campylobacter and Salmonella.
An acute illness with vomiting and/or diarrhoea (three or more loose stools per day).
Toxin-related illnesses may present with clinical features additional to and dominant to the gastrointestinal clinical features. These may include neurological (change in sensation, muscle weakness, difficulty swallowing), dermatological (itch and flushing), musculoskeletal (painful muscles and joints) and cardiovascular (hypotension and bradycardia) features.
Laboratory test for diagnosis
Laboratory definitive evidence for a confirmed case requires isolation of the specific organism or detection of organism nucleic acid or detection of toxin.
Note: For some pathogens, detection of nucleic acid is insufficient to meet the case definition (isolation is required) – see specific notifiable enteric diseases chapters, eg, Shigellosis.
- Under investigation: A case that has been notified, but information is not yet available to classify it as probable or confirmed.
- Probable: A clinically compatible illness.
- A clinically compatible illness accompanied by laboratory definitive evidence, or
- A clinically compatible illness and a common exposure associated with a laboratory confirmed case.
- Not a case: A case that has been investigated and subsequently found not to meet the case definition.
Notification is required for single cases of chemical, bacterial or toxic food poisoning such as botulism, histamine (scombroid) poisoning and toxic shellfish poisoning (any type).
In addition to the specific enteric diseases covered in other chapters, the following categories of acute gastroenteritis must be reported without delay:
- any suspected outbreak of acute gastroenteritis where there is a suspected common source (for example, two or more cases associated in time or place, commonly caused by norovirus, rotavirus, enteric adenoviruses, B. cereus, S. aureus)
- single cases in a high-risk category (food handler, early childhood service worker, or other person at increased risk of spreading infection)
- single cases of infectious gastroenteritis of public health importance, not listed on schedule (1) as individually notifiable, including but not exclusive to:
- E. coli strains causing diarrhoea, for example, enteropathogenic E. coli (EPEC) and enterotoxigenic E. coli (ETEC)
- Clostridium perfringens
- Vibrio parahaemolyticus.
- single cases caused by non-infectious gastrointestinal intoxicants (for example, fish or shellfish toxins; use of aluminium, copper or brass utensils to store acidic fruits or drinks; barbecued food where tanalised wood has been used).
Management of case
Obtain a history of possible contacts, travel, food and water ingestion, in addition to any reported with the notification.
Ensure that laboratory confirmation by stool testing, when appropriate, has been attempted. Testing of stool (or vomit, although yield is lower than from stool) samples for norovirus should be considered in an outbreak situation where the clinical and epidemiological features suggest norovirus infection. Unfortunately, the rapid progress of most norovirus outbreaks and relatively long turnaround time for norovirus testing necessitate empirical diagnosis and management for at least the first 5–7 days in most of these events.
In a health care facility, place patients with acute gastroenteritis of unknown cause under contact isolation precautions. If the cause of gastroenteritis is known, isolation precautions are only necessary for those infections with the potential for person-to-person spread. For example, all patients with norovirus and diapered or incontinent patients with rotavirus or enteric adenovirus infections require contact isolation for the duration of symptoms. Consider placing such patients, especially if vomiting, under airborne precautions in addition to contact precautions.
Food handlers with gastroenteritis of unknown cause should be withdrawn from food handling work while undergoing investigation and until symptoms resolve; they may be able to continue working as long as that work does not involve handling food. There is no additional restriction on food handlers found to have non-cholera vibrio infections, or shellfish or fish poisoning. For further details, refer to the exclusion and clearance criteria in Appendix 2: Enteric disease.
Advise the case and/or caregivers of the nature of the disease and its mode of transmission. Educate about hygiene, especially hand cleaning.
Management of contacts
A person who has been exposed to an infected person or infectious material in such a way that transmission may have occurred.
For people known to have eaten C. botulinum toxin-containing food, consult an infectious diseases specialist. Also, Botulinum antitoxin may be recommended for close contacts who may have shared the implicated food with the case in the previous 72 hours following consultation with an Infectious Diseases specialist and the Ministry of Health.
Advise all contacts of the incubation period and typical symptoms of the disease, and to seek early medical attention if symptoms develop.
Other control measures
Identification of source
Check for other cases in the community. Investigate potential food, water, or other common sources of infection (eg, young animals and farm animals) if there is a cluster of cases, an apparent epidemiological link or a single case of suspected botulism. When appropriate, collect specimens of suspect foods for analysis, ensuring samples are transported in sealed containers.
If indicated, check water supply for microbiological contamination and compliance with the latest New Zealand drinking-water standards (Ministry of Health 2008).
Clean and disinfect surfaces and articles soiled with stool. For more details, refer to Appendix 1: Disinfection.
Educate the public about hand hygiene and safe food preparation (see Appendix 3: Patient information) and the risks posed by exposure to farm animals and their wastes.
If a water supply is involved, liaise with the local territorial authority to inform the public. Advise on the need to boil water.
In early childhood services or other institutional situations, ensure satisfactory facilities and practices regarding hand cleaning; nappy changing; toilet use and toilet training; preparation and handling of food; and cleaning of sleeping areas, toys and other surfaces.
For suspected or known norovirus outbreaks, refer to Guidelines for the Management of Norovirus Outbreaks in Hospitals and Elderly Care Institutions (Ministry of Health 2009).
Ensure complete case information is entered into EpiSurv.
If a cluster of cases occurs, contact the Ministry of Health Communicable Diseases Team and outbreak liaison staff at ESR, and complete the Outbreak Report Form.
Where food/food businesses are thought to be involved inform the Ministry for Primary Industries and the local territorial authority as appropriate.
- ESR. 2012. Guidelines for the Investigation and Control of Disease Outbreaks. Porirua: Institute of Environmental Science and Research Limited.
- Ministry of Health. 2008. Drinking-water Standards for New Zealand 2005 (Revised 2008). Wellington: Ministry of Health.
- Ministry of Health. 2009. Guidelines for the Management of Norovirus Outbreaks in Hospitals and Elderly Care Institutions. Wellington: Ministry of Health.