Chapter last reviewed and updated in December 2018. A description of changes can be found at Updates to the Communicable Disease Control Manual.
New Zealand Epidemiology
Human immunodeficiency virus (HIV) acts by depleting the body’s normal immunological defense mechanism. Acquired immunodeficiency syndrome (AIDS) is the late stage of the spectrum of HIV disease.
HIV became notifiable in New Zealand in 2017. Voluntary surveillance was undertaken between 1985 and 2017. AIDS has been a notifiable condition in New Zealand since 1983.
HIV infections in New Zealand are mostly concentrated in men who have sex with men (MSM) and heterosexually infected individuals from sub-Saharan Africa and South-East Asia. In MSM infection is largely due to transmission in New Zealand.
For the most up-to-date information on the epidemiology of HIV and AIDS in New Zealand, refer to AIDS – New Zealand, the newsletter produced by the AIDS Epidemiology Group (AEG), which is also posted on the Te Whatu Ora website.
The purpose of HIV surveillance is to:
- understand disease burden (to inform planning, policy development, prioritisation and resource allocation)
- identify emerging problems and outbreaks or clusters of disease
- evaluate the effectiveness of policies and programmes.
For surveillance purposes, in New Zealand:
- An individual is reported with newly acquired HIV when they have first tested positive on a laboratory test, as detailed below.
- An individual is reported with previously acquired HIV when they have previously been diagnosed with HIV overseas, have no record of an earlier diagnosis in New Zealand, and are having a first viral load test (for monitoring of their infection) in New Zealand.
Laboratory testing for diagnosis of HIV
Laboratory definitive evidence of HIV infection in an individual aged 18 months or older requires:
- a repeatedly reactive result on an initial antigen/antibody combination immunoassay that detects HIV-1 and HIV-2 antibodies or HIV-1 p24 antigen and a reactive result on an HIV-1/HIV-2 antibody differentiation immunoassay
- a repeatedly reactive result on an initial antigen/antibody combination immunoassay that detects HIV-1 and HIV-2 antibodies or HIV-1 p24 antigen and a reactive result on the HIV-1 nucleic acid test (NAAT) test.
Laboratory definitive evidence of HIV infection in an individual aged under 18 months requires:
- a repeatedly reactive result on the NAAT test on specimens taken at two different dates.
- Under investigation: A case that has been notified, but information is not yet available to classify it as confirmed or not a case.
- Probable: Not applicable.
- Confirmed: Laboratory definitive evidence of HIV infection.
- Not a case: A case that has been investigated and subsequently found not to meet the case definition.
Spread of infection
Within two to four weeks after infection, people may experience a flu-like illness with generalised lymphadenopathy which may last a few weeks.
Without treatment, the time from initial infection with HIV to clinical onset of AIDS in an untreated patient is variable, averaging 8–10 years in developed countries.
Mode of transmission
HIV is transmitted from person to person in four main ways:
- through anal or vaginal sex
- through the sharing of contaminated injecting equipment (needles and syringes)
- from an infected mother to her baby during pregnancy or childbirth or through breastfeeding
- through transfusion of infected blood or blood components and the transplantation of infected tissue or organs.
Period of communicability
While transmission of HIV can occur throughout an infected person’s life, the transmissibility varies with the viral load, which is typically high during initial seroconversion and later as the CD4 count falls. Anti-retroviral therapy that successfully suppresses the circulating viral load to low or undetectable levels greatly reduces infectivity.
HIV is a notifiable condition. New laboratory diagnoses are notified to the local Medical Officer of Health via the secure web-based EpiSurv portal administered by ESR (the Institute of Environmental Science and Research) using non-identifiable data. Acceptance of the incoming e-notification by the local public health service will automatically result in the AEG receiving access to the information, and in creation of a web-based notification form. The AEG will send the health provider who ordered the laboratory test a link to this form for the health provider to complete online.
Section C of Part 1 of Schedule 1 of the Health Act 1956 covers notification of AIDS, HIV and other sexually transmitted infections. Under this legislation, the notification process must not include identifying information.
The AEG makes confidential quarterly reports to the Ministry of Health and Medical Officers of Health. It produces the AIDS – New Zealand newsletter annually and disseminates it widely, to stakeholders and the public.
Management of case
Identify the mode of infection in consultation with the attending infectious diseases physician.
No isolation precautions other than standard precautions are needed for HIV-positive cases in health care facilities. Staff who are asked to perform an invasive procedure on the case are commonly informed about the case’s infectious status. In almost all cases, there are no restrictions on attending work, early childhood services or schools or other community activities.
The case should be under the care of a physician or paediatrician who has a special interest in HIV and AIDS.
People found to be infected with HIV should receive counselling on the implications of the diagnosis from a medical practitioner and/or counsellor. The counselling should cover the practical and legal aspects of preventing transmission of HIV. Specific recommendations include:
- not donating blood
- not sharing drug-injecting equipment
- not sharing razors or toothbrushes
- following safe sex practices and informing sexual partners
- informing health care workers (including dentists) of infection.
Management of contacts
- sexual or needle-sharing partners of an HIV-infected person
- individuals who have suffered a sharp injury with an object contaminated with HIV-infected blood or body fluid
- newborn babies whose mothers are HIV-positive
- individuals who have received HIV-infected body fluid (eg, blood, semen or cerebrospinal fluid) splashes to a mucosal surface or area of broken skin.
All investigation and treatment, including management of HIV-infected pregnant women, should be undertaken under the supervision of an infectious diseases physician with a special interest in HIV.
Health practitioners must perform all HIV tests with the informed consent (verbal consent is sufficient in most cases) of the person, and with pre-test counselling that covers the reason for the test, the person’s right to decline testing, the date and means by which the results will be made available and an assurance that the practitioner will take steps to maintain confidentiality, including an offer to test under code. More comprehensive pre-test counselling is indicated when the person is at high risk of being HIV-positive.
When considering post-exposure prophylaxis, practitioners should seek immediate advice from the infectious diseases service of the closest tertiary care hospital. An anti-retroviral prescriber must authorise the prophylaxis.
The need for anti-retroviral prophylaxis depends on:
- the period that has elapsed between the exposure and the availability of appropriate treatment (chemoprophylaxis has been shown to have some protective effect up to 36 hours after exposure)
- the type of exposure and source material (eg, a needle-stick injury or sexual contact).
Health practitioners should offer the contact comprehensive counselling, ideally in conjunction with the supervising infectious diseases physician. The New Zealand AIDS Foundation is the lead Ministry of Health non-governmental agency for HIV and AIDS.
Other control measures
Identification of source
If there is a cluster of cases, investigate for a common exposure, including through sexual contact, sharing of injecting drug equipment, health care or skin penetration practices (eg, tattooing). If the case could be transfusion-related, contact the New Zealand Blood Service.
Clean equipment and surfaces potentially contaminated with blood or body fluids. For further details, refer to Appendix 1: Disinfection.
Advise injecting drug users on single-use injecting equipment. Needle and syringe exchange programmes exist in pharmacies and community groups throughout New Zealand. A list of outlets is available from the New Zealand Needle Exchange Programme website.
The Ministry of Health offers an HIV screening programme for all pregnant women. Information is available on the National Screening Unit website.
- Centers for Disease Control and Prevention and Association of Public Health Laboratories. 2014. Laboratory testing for the diagnosis of HIV infection: Updated Recommendations. (Accessed 1 November 2018)
- Dickson N, Lee B, Foster T, et al. 2015. The first 30 years of HIV in New Zealand: Review of the epidemiology. New Zealand Medical Journal 128(1426): 31–48.
- Joint United Nations Programme on HIV/AIDS and World Health Organization. 2000. Second generation surveillance for HIV: The next decade [PDF, 278 KB]. WHO/CDS/CSR/EDC/2000.5.(Accessed 1 November 2018.)
- UNAIDS/WHO Working Group on Global HIV/AIDS and STI Surveillance. 2013. Guidelines for second generation HIV surveillance: an update: Know your epidemic. (Accessed 1 November 2018.)