HIV is 'spread most' by people with medium levels of the virus

People with medium levels of HIV in their blood are most likely to contribute to the spread of the virus, a new report has claimed.

The study, undertaken by researchers from Imperial College London, found that those with a lower 'viral load', the amount of the HIV virus in their blood, took longer to progress to the symptoms of AIDS and as such may have more opportunity to transmit the disease to other people.

At the same time the study also discovered that HIV-sufferers with a higher viral load were more infectious but also had a shorter life expectancy and therefore had less time to contribute to the spread of HIV.

Dr Deirdre Hollingsworth, one of the paper's authors from Imperial College London, said: "Just being highly infectious isn't enough, you have to live long enough to pass the virus on. This long-term view should inform public health policy."

And her colleague, Dr William Hanage, added: "It's certainly very striking that the viral loads we see most in nature are just right to make sure the virus gets transmitted as much as it can before it kills its host, which is what you would expect from evolution."

According to figures published by the World Health Organization, 4.3 million more people were infected with HIV in 2006, 65 per cent of whom lived in sub-Saharan Africa.

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