Important note: Information in this article was accurate in 2005. The state of the art may have changed since the publication date.
Mail & Guardian (Johannesburg) - September 16, 2005
Belinda Beresford
This is in contrast to the idea of a rolling tsunami of infections, with HIV-positive people spreading the epidemic throughout the long asymptomatic "chronic" stage of HIV.
The new paradigm suggests different techniques are needed to control the spread of the disease. In particular, they must counter the deficiencies of the standard HIV test, which generally fails to pick up carriers when they are at their most infectious -- within the first few weeks of contracting the virus.
Ground-breaking research in Johannesburg's Hillbrow, where the HIV prevalence is estimated at between 20% and 40%, aims to provide new approaches to the problem of acute infection.
The idea of spikes of transmission around newly infected individuals is supported by evidence that roughly half the HIV transmissions between established couples occur within the first six months of one partner becoming infected.
During acute infection, subjects have viral loads hundreds of times higher than they will ever have again -- even in the terminal stages of Aids.
Yet routine tests can register "false negatives" in such cases. To date, fewer than 1 000 people of an estimated 60-million people infected with the disease have been detected with acute HIV infection. Some do suffer "seroconversion illness", but the symptoms tend to be mild and non-specific -- fever, tiredness, headaches, or a rash.
In standard tests, it can take several weeks for an attacked immune system to produce sufficient antibodies to register. PCR (polymerase chain reaction) tests, which look for the nucleic acid of the virus itself, can detect infection within a few days of occurrence. But they are costly.
Recent studies have thrown a spotlight on the problem. Research in Malawi found that 5% of men attending clinics for symptoms of sexually transmitted diseases were in the acute stage of HIV infection, yet were given the all-clear after testing negative on standard antibody tests.
Confirming this is a study of 2 000 people attending the Esselen Street clinic, which services Hillbrow's youngish, mostly male population.
Wits University's Reproductive Health and HIV Research Unit and the National Health Laboratory Services (NHLS) found 12 cases of acute infection which had tested negative.
Said the unit's Fran ois Venter: "This means that one in 200 people walk through the door in the acute stages of HIV infection. We know they are having sex -- eight out of 12 are coming from the sexually transmitted disease clinic, and the other four have chosen to come for counselling and HIV testing. Yet, they're being told they don't have HIV, at the most infectious point of their lives. It's a huge challenge."
Identifying temporarily hyper-infectious people and their recent sexual partners -- who in turn may be hyper-infectious -- could prove the key to reining in the spread of the epidemic.
The blood samples used in the study were anonymous and unlinked, meaning they could not be traced to individuals. However, the same teams are about to start a new study in Hillbrow aimed at detecting seroconverters -- but with patients knowing the results of their tests.
The group hopes to find at least one acute HIV case per month, testing between fifty and a hundred people.
The new study has two areas of focus: to develop different HIV tests which will eliminate or reduce the window period and to look at different ways of using existing tests.
The team, led by Wendy Stevens at the NHLS, has piloted an innovative pooling technique, involving just 103 PCR tests to detect the 12 acute HIV infections -- bringing an elevenfold cost reduction compared to testing individually.
The method still costs about R1 000 per person identified. However, this has to be measured against the opportunity to intervene and prevent further infections.
The other area of research aims to determine what was distinctive about the sexual activity that led to infection, and what interventions will discourage highly infectious patients from engaging in sex. It offers the possibility of tracing back sexual partners and possibly detecting other newly infected people.
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