The implications of variability

Does subtype affect disease progression?

A study presented in 2006 found that Ugandans infected with subtype D or recombinant strains incorporating subtype D developed AIDS sooner than those infected with subtype A, and also died sooner, if they did not receive antiretroviral treatment. The study's authors suggested that subtype D is more virulent because it is more effective at binding to immune cells.⁵ This result was supported by another study presented in 2007, which found that Kenyan women infected with subtype D had more than twice the risk of death over six years compared with those infected with subtype A.⁶ An earlier study of sex workers in Senegal, published in 1999, found that women infected with subtype C, D or G were more likely to develop AIDS within five years of infection than those infected with subtype A.⁷

Several studies conducted in Thailand suggest that people infected with CRF A/E progress faster to AIDS and death than those infected with subtype B, if they do not receive antiretroviral treatment.⁸