HIV-infected people with a lower amount of the virus in their blood have the potential to infect more people than those with a high viral load, suggests new research.

The study was published last week (22 October) in the Proceedings of the National Academy of Sciences.

Dutch and UK scientists analysed data from untreated groups of people infected with HIV in Holland, Uganda and Zambia.

They found that individuals with an intermediate viral load — typical of the asymptomatic stage after infection and before the onset of AIDS — have a better prognosis and hence more opportunity to transmit the virus to others before they progress to AIDS.

This is despite the fact that individuals with higher viral loads are more infectious, they write.

The researchers conclude that targeting antiretroviral therapy at people with the highest HIV viral loads, even though they are likely to have the most severe infection, is "misguided".

Thumbi Ndung'u from the University of KwaZulu-Natal's Nelson Mandela School of Medicine in South Africa, says, "The public health implications are staggering."

He told SciDev.Net the results could lead to a paradigm shift in the way in which public health practitioners view asymptomatic chronic HIV infection. "We may have to treat massive numbers of asymptomatic HIV infected individuals not previously thought to require treatment," said Ndung'u.

The research indicates that the HIV virus may have evolved to attain an ideal balance between infectiousness and virulence, to ensure a maximum infection rate over the lifetime of the infected person.

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