In the last few years it has become evident that treatment with antiretroviral drugs during the early weeks of infection may have a significant effect on the course of HIV infection.

Exposure in the past 24-48 hours

Some hospitals are now offering what is called post–exposure prophylaxis (PEP) to people no more than 24 to 48 hours after a possible exposure to HIV. This may have the potential to block HIV infection completely if treatment lasts one month. Treatment does not need to continue for longer than one month because the aim of treatment is to prevent HIV from entering cells in the body. Infection will either become established or it will be stopped within that period.

Recent guidance from the Department of Health suggests PEP should be offered to healthcare workers exposed through needle stick injuries within one hour of exposure for maximum effectiveness.

A study of people exposed to HIV–infected blood through needlestick injuries showed that treatment with the drug AZT 24 hours after exposure reduced the risk of infection by 80%.

Clinics will not automatically offer this form of treatment to everyone who believes they have been at risk of HIV infection. They may use a number of questions to decide whether you have been at high risk of infection, such as:

• Was your partner known to be HIV–positive?
• Was your partner in a high-risk group?
• Did ejaculation occur into your body, or were you the active partner?
• Did you inject a large quantity of blood into your veins if you were sharing needles?
• Was sexual intercourse violent or traumatic e.g. sexual assault?
• Where did your partner come from? A metropolitan area with high HIV prevalence or a small town with low prevalence?
• Are you able to adhere to a four-week course of treatment which might produce unpleasant side-effects?

You will need to take medication according to a strict dosing schedule.

It's essential that this treatment begins no more than 24–48 hours after exposure for it to offer the maximum chances of success.

Of course, it may be the case that you will not be infected with HIV even if you do not take the drugs available. But it will not harm you if, on the other hand, you take the drugs and turn out not to have been exposed to HIV in the first place.

See HIV transmission: post-exposure prophylaxis for more information on this subject. The use of post-exposure prophylaxis for sexual transmission is discussed in Developing prevention technologies.

Exposure more than 48 hours ago

In people exposed to HIV infection more than 24–48 hours prior to seeking medical attention, and where signs of HIV infection have been detected, many doctors are now interested in the possibility of offering three or four antiretroviral drugs in combination as a means of limiting the spread of HIV in the body. Interfering with virus copying at this stage of infection may offer an opportunity to eradicate HIV from the body after several years of treatment, or to maintain infection at an extremely low level for the rest of your life.

In such cases doctors may wish to test for traces of HIV itself to see whether such a course of treatment is worthwhile.

HIV p24 antigen testing can detect HIV infection within two to three weeks of infection. It is generally available as part of combination antibody/antigen tests; if one of these is positive but confirmatory antibody tests are negative, then either another p24 test or a viral load test can be done.

Viral load testing can detect the presence of HIV genetic material before antibodies have been developed. Some clinics may also carry out an HIV genome test which looks for the existence of proviral DNA. The benefit of HIV DNA or HIV RNA testing during suspected acute (early) infection is to reduce the period of diagnostic uncertainty and facilitate very early treatment.

There are other ways in which it may be possible to distinguish very recent infection with HIV from long-established infection: see the discussion of Detuned tests in The scientific basis of HIV antibody testing.

At the moment it is recommended that treatment administered during primary infection should continue indefinitely.

Some people may develop symptoms during this phase of infection before antibodies appear in the blood. Antibodies usually become detectable at the same time as this illness. This is known as seroconversion illness. The symptoms include:

• Prolonged fever (4 – 14 days) and aching limbs.
• Red blotchy rash over the trunk.
• Sore throat (pharyngitis).
• Ulceration in the mouth or genitals.
• Diarrhoea.
• Severe headaches.
• Aversion to light.

Other symptoms, such as paralysis, meningitis and opportunistic infections as a consequence of severe immune suppression are much less common. Symptoms of seroconversion may occur in up to 80% of people infected, but the severity of the symptoms varies. Some people report only a mild flu–like illness 30–60 days after a risk of HIV exposure, but others experience an illness severe enough to require hospitalisation. The longer the illness lasts, and the more severe it is, the more likely you are to develop AIDS within five years.

Remember that these symptoms could be caused by other infections; flu, glandular fever, tonsillitis and a serious herpes attack have similar symptoms to those reported in seroconversion illness.

If you think that you have been exposed to HIV in recent weeks and you develop some of these symptoms, treatment is an option that should be considered. However, we don't yet know whether this treatment will be of long–term benefit. If you want to begin such treatment, you should approach one of the major HIV treatment centres immediately. Do not wait to be referred by your GP, who may not understand the urgency of the need for treatment or the scientific rationale for intervening with drug treatment at this stage of infection. Some of the largest GUM clinics in London are now running studies to follow people treated at this stage of infection. If you live outside London call your local clinic and ask to speak to a consultant to find out whether they will consider embarking on an experimental course of treatment.