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African AIDS "is not caused by a more virulent strain"

April 2001

In April 2001, researchers announced that they have concluded the epidemic of HIV in Sub-Saharan Africa is not caused by a more virulent strain of the virus but is more probably due to political and socio-economic factors.

The main virus subtypes in Sub Saharan Africa are 'A, C, D', compared to Europe and USA where 'B' is more prevalent. Worldwide there are more than 160 subtypes. The more severe nature of the epidemic in Africa plus the existence of numerous variants around the world has fueled speculation that some types are more infectious than others.

Professor Ronald Gray, of the Johns Hopkins School of Public Health in Maryland, and his colleagues after calculating the probability of HIV transmission per sexual act among monogamous couples in Uganda concluded that infectiousness was the same for most subtypes of the virus. "The infectivity of the virus in Africa is comparable to what we see in Europe and North America."

The rapid spread of the virus in Africa could be attributed to the social and political upheavals that have taken place on the continent, including numerous wars, movements of refugees, breakdown of social barriers leading to mass rape amongst many others.

The exception to these new findings may be West Africa where generally the rates of HIV infection are much lower than the rest of the continent. West Africa is home to HIV2 which is less virulent than the more common HIV1 virus found elsewhere. The region also has more recombinant HIV viruses, which are not a clear subtype of HIV. Research suggests recombinant viruses are less infectious

Two factors were found to contribute to infectivity were viral load, the amount of the virus circulating in the blood, and genital ulcerations Gray reported in the Lancet Medical journal. Age was another factor associated with increased chances of transmission, the younger the person the greater the probability of infection.The researchers concluded it was not due to frequency of sexual contact because they had controlled for this. The researchers speculated that partial immunity or selective resistance generated in older individuals due to repeated exposure to infection may account for this.

Gray went on to say "Scientifically, the evidence that the HIV viral load is a critical determinant is of very profound importance for further control strategies. That has not been shown before. Antiretroviral drugs that reduce the level of the virus in the body could help to reduce infectivity."

(Adapted from African AIDS 'Not Caused by More Virulent Strain' April 12, 2001 by Patricia Reaney LONDON (Reuters) )
Probability of HIV-1 transmission per coital act in monogamous, hetereosexual,HIV-1 discordant couples in Rakai, Uganda
Gray et al; The Lancet; Vol 357, April 2001

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