New strain of HIV beats blood tests

A NEW strain of the Aids virus has emerged that cannot always be detected by the tests used to screen donations to the blood transfusion service.

Health officials in Britain and France have asked manufacturers of blood tests for HIV antibodies to re-evaulate them urgently to ensure that the new strain cannot contaminate blood supplies. One French- made test has already been withdrawn.

Professor John Cash, director of the Scottish Blood Transfusion Service, said he had contacted Murex, which makes the test kit most commonly used in Britain, on hearing of the outbreak of a new strain of HIV in France. Philip Mortimer, a virologist at the Government's Public Health Laboratory Service near London, said he will meet Murex next week to discuss the problem. 'We're concerned but it's primarily a problem for the transfusion service,' he said.

Scientists from Murex, which now makes the HIV test kit originally developed by the Wellcome drug company, flew to Paris two weeks ago for briefings with Francois Simon, a virologist at the Bichat Claude Bernard Hospital who identified the new HIV strain in 10 French Aids patients. A spokesman for Murex would not comment.

Dr Simon said that the Murex test kit used in Britain had incorrectly given negative results in two out of the 10 patients. The remaining eight results were 'weakly' positive and therefore ambiguous, he said. Belgian scientists have also reported one case of an Aids patient with the new HIV strain.

The French health authorities have ordered one French- made HIV test to be withdrawn and has begun an urgent reappraisal of all others to ensure they can detect the presence of antibodies to the new HIV strain.

Scientists first identified the strain, which they call group O, a few years ago in people living in the Cameroon in west Africa. An analysis in the Journal of Virology last month showed it is still part of the HIV-1 family, but at its 'outer fringes', according to Gerald Myers, director of a project to study HIV types at the Los Alamos National Laboratory in the United States.

Current tests - which use synthetic pieces of HIV to identify antibodies in the blood - appear to be too specific for typical members of the HIV-1 family, making them less able to detect mutant variants such as the group O viruses.

The problem is reminiscent of the decision in 1990 to introduce tests for HIV-2, the second leading family of HIVs, as a result of the accidental discovery that a blood donor in Britain was infected with it.

Prof Cash emphasised that, before their blood is used, all donors are asked whether they have ever visited Africa or had sex with someone from there. This is the first line of defence against contamination with a mutant strain of HIV, he said.

Dr Simon said that of the 10 French patients with the group O strain of HIV, nine had lived in the Cameroon, where between 5 and 10 per cent of HIV positive people are infected with the group O strain.

The tenth was a French woman who worked as a barmaid in eastern France. Although she had never been to Africa, she lived in a garrison town where some of the soldiers may have spent time in the Cameroon.

Dr Simon emphasised that the risk of a blood donor being infected with group O HIV in Britain or France is 'very, very low'.

Blood tests on cows belonging to a Cheshire dairy farmer have confirmed that an Aids-like virus could be responsible for an outbreak of unexplained illnesses in the herd.