Their finding is based on a study of 300 people in Uganda, infected between 1995 and 2001. It was presented at the 2006 Conference on Retroviruses and Opportunistic Infections in Denver, Colorado, last week.
About 50 of the patients were infected with HIV subtype A, 200 with subtype D and the rest with a cross between the two.
Viral subtype was found to be a predictor of survival. But viral load, the conventional measure of HIV progression, was the same across subtype groups.
People with subtype D or the recombinant strain died significantly earlier than those infected with other strains. Average survival time was 8.8 years for subtype A, but just 6.9 for subtype D and 5.8 for the recombinant strain. Ten per cent of people infected with subtype D died within three years.
In Uganda and other parts of Africa, subtype D makes up 10 per cent of HIV cases. Subtypes A and B dominate in the UK.
Researchers believe subtype D and the combined strain are more virulent because they can bind to a receptor on the surface of immune cells that subtype A cannot. This means AIDS develops more quickly.
