New HIV may not show up in tests

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AIDS RESEARCHERS are urging the Government to fund more work on analysing new strains of HIV in Britain as scientists revealed that a new type of virus has emerged that may go undetected by present blood tests.

French scientists have identified a new class of Aids virus in a woman from Cameroon, West Africa. It does not belong to the two main types of HIV-1 and the researchers say it is likely to escape detection by existing HIV tests. It was detected by Francois Simon, a virologist at the Bichat Hospital in Paris, who found it was so different to all other strains of HIV-1 that he had to classify it as belonging to a separate type.

Aids scientists in Britain said they have tried to convince medical authorities to monitor the emergence of sub-types of HIV. The government's Public Health Laboratory Service in north London is responsible for monitoring the spread of HIV in Britain but it analyses only two new infections a month for sub-type information.

Scientists at the laboratory warned two years ago that it was necessary to increase the sampling programme to 50 tests a month. ''Two a month is not giving us a wide enough picture. We should attempt to subtype as many as we can so we can say what's happening around the country,'' one PHLS scientist said in 1996.

A strain of HIV called subtype E has already appeared in Britain as a result of tourists becoming infected after visiting Thailand, where the E-sub-type is responsible for an Aids epidemic among heterosexuals.

Andrew Leigh-Brown, head of the centre for HIV research at Edinburgh University, said that keeping track of different HIV sub-types would help to identify new routes of transmission between this country and abroad.

''I think this sort of research programme could be highly informative but it has been increasingly difficult to find financial support for this type of work,'' Dr Leigh-Brown said.

Some scientists believe certain sub-types of HIV may exhibit different properties, which make them either more lethal or more easily transmitted. One study, for instance, found that sub-type E of the virus may be more likely than other subtypes to be spread during heterosexual intercourse.