First establish what happened
Take a detailed history of the incident e.g. what sexual activity took place, whether it was consensual, details of
injecting drug use.
It is preferable to use medical terminology when discussing sexual practices and sexual health, however it is important
that the patient understands the terminology used. Conversely, the clinician should ask for clarification of any colloquial
terminology they are unfamiliar with. A non-judgemental attitude will help to ensure that any risky behaviours are fully
See BPJ 20 (April 2009), Let’s
talk about sex.
If possible, find out any details that are known about the person who is the source of potential HIV exposure. If the
patient does not know the source’s HIV status and contact details are available, establish whether the patient or
practice will attempt contact.
Check clinical history
- Has the patient had any previous HIV tests?
- Does the patient have any current or previous STIs?
- Check hepatitis B and hepatitis C status – recent tests or immunisation
- Consider taking a psychiatric, drug and alcohol history
Assess risk of HIV transmission
The risk of HIV transmission is determined by:3
- Method of exposure
- Risk that the source is HIV positive
- Co-factors associated with increased risk of transmission from the source to the exposed person
Method of exposure. The risk of HIV transmission with sexual contact is difficult to quantify as there
are many additional factors that influence risk such as concurrent STIs or other genital conditions, cervical or anal
dysplasia and circumcision status.4 The highest risk behaviour is receptive anal intercourse without a condom
with a person known to be HIV positive (Table 1). Oral intercourse poses the lowest risk but HIV may very rarely be transmitted
by this method of exposure, particularly when there is a breach in oral mucosal integrity.4
Source status. If possible, the source should be contacted to establish their HIV status. If they do
not know their status, request that they be tested.
If the source is unable to be contacted or they refuse to disclose their status, the risk that they are HIV positive
is based on seroprevalence (Table 2).
The United Nations AIDS organisation has information on worldwide prevalence
of HIV and AIDS.
Co-factors that increase risk of transmission3
- High viral plasma load in source – a person is most infectious when they first contract the virus and when they
have AIDS related symptoms
- STI in either the source or exposed person, especially genital ulcer disease and symptomatic gonococcal infections
- Breach in genital mucosal integrity e.g. trauma or genital tract infection
- Breach in oral mucosal integrity (in relation to oral sex)
- Exposed male is uncircumcised (inner mucosa of foreskin is more susceptible to infection and tears)
Management and referral
The role of the GP is to establish whether there has been significant risk of exposure to HIV. If this is the case,
the patient should be referred immediately to an infectious diseases or sexual health physician with HIV experience. HIV
testing and follow-up care takes place within this setting.
Non-occupational post exposure prophylaxis
Antiretroviral drugs may be prescribed for people who have had a significant risk of HIV exposure, to reduce the possibility
of acquiring the infection. Non-occupational post exposure prophylaxis (NPEP) ideally should be started within a few hours
of the exposure and no more than 72 hours later, as it is very unlikely to be effective after this time.
The use of NPEP is still controversial as there is currently limited evidence that it reduces the transmission of HIV
and concern that it may encourage risky behaviour. It is also very costly ($1000 – $1500 per month) and adherence
may be an issue due to the length of treatment required (28 days) and potentially serious adverse effects of the drugs.6
NPEP is currently not funded in New Zealand. PHARMAC has assessed an application for this indication and it is currently
being considered alongside other funding priorities. Post exposure prophylaxis is funded by special authority for occupational
exposure (e.g. needle stick injuries) and in some cases of sexual assault (usually covered by ACC).
If NPEP is being considered, the patient should be referred urgently to an infectious diseases consultant. PHARMAC has
published a list of named specialists that have been approved to prescribe antiretrovirals in New Zealand.
See the Pharmaceutical Schedule Update, 1 January 2009, Page 4. Also available online at
Indications for NPEP
NPEP may be considered if the source is known to be HIV positive or the source status is unknown, but they are from
a high-risk population, which includes:4
- Men who have sex with other men
- Men who have sex with both men and women
- Injecting drug users
- People from a country where HIV is prevalent
- Commercial sex workers
- People who have a sexual partner belonging to any of these groups
And there has been:
- Receptive or insertive anal or vaginal intercourse
- Shared drug injecting equipment
A clinician considering prescribing NPEP would usually calculate the risk of infection, based on the type of exposure
and the risk of infection in the source (see Tables 1 and 2). In general, NPEP is considered if the transmission risk
is greater than 1 in 15000.3
Examples of risk calculation–
- Receptive anal intercourse with MSM source of unknown HIV status in Auckland:
Unprotected receptive anal intercourse (1/120) x MSM in Auckland (10%) = 1/1200
- Sharing of drug injecting equipment with an HIV positive source:
Use of contaminated injecting equipment (1/150) x HIV positive source (100%) = 1/150
- Insertive vaginal intercourse with a sex worker of unknown HIV status:
Insertive unprotected vaginal intercourse (1/1000) x female sex worker in New Zealand (1%) = 1/100000
For NPEP, a two or three drug regimen is prescribed for a course of 28 days.
The commonly recommended drug regimen for NPEP is zidovudine + lamivudine (Combivir) plus either efavirenz (Stocrin)
or lopinavir + ritonavir (Kaletra). Clinicians may select a different drug combination, depending on specific patient
factors related to the treatment history of the source patient (if known), or the risk of adverse effects.4
If the patient is being referred immediately to specialist care, HIV testing will not be required by the GP. Otherwise,
an HIV test (HIV antibody) should be requested immediately, and testing will need to be repeated regularly (see follow
up below) as it can take up to six months for infection to be detected.7
Assess pregnancy risk and consider the emergency contraceptive pill if required.
Test for Hepatitis B, Hepatitis C and STIs (chlamydia, gonorrhoea, syphilis, depending on exposure history).
- HIV repeat testing at four to six weeks, three months and six months after exposure4
- Provide support when discussing HIV test results
- STI repeat testing at four to six weeks and three months as appropriate
- Hepatitis C repeat testing (if indicated) at four to six weeks, three months and six months after exposure4
- Offer Hepatitis B vaccination if infection has been ruled out.
- Discuss precautions e.g. use condoms, avoid sharing blood-contaminated fomites (razors, toothbrushes) until final
negative test at six months4
- Reinforce safer sex messages
If the patient is receiving NPEP, they will require ongoing assessment for adverse effects as well as LFT, CBC and electrolyte
monitoring. Responsibility for this should be established with the prescribing physician.