At least one in six patients maintains a viral load over one hundred thousand

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A study of patients in southern Africa diagnosed during primary HIV infection has found that one in five maintained viral loads over 100,000 copies/ml for at least 400 days after infection. One in six will maintain such a persistent high viral load for three years or more, researchers calculated.

Quantifying the percentage of patients who, off treatment, maintain high viral loads is important for calculating the likely transmission rate within a population and the prevention impact of treating them. Another study presented at the 18th Conference on Retroviruses and Opportunistic Infections (CROI) last week found that an individual with a viral load of 100,000 copies/ml is likely to transmit HIV nearly three times more often than a person with a viral load of 10,000 copies/ml.

The southern African study, from Vladimir Novitsky and colleagues from Harvard Medical School, also found that patients with viral loads over 100,000 copies/ml experienced dramatically faster declines in their CD4 counts.

The study looked at 75 patients from Durban in South Africa and Gaborone in Botswana who were diagnosed while they had acute HIV infection (defined as within 30 days of the estimated date of infection). These 75 patients were followed for an average time of 573 days and had an average of four viral load tests during that time.

The researchers found that one-third of the patients maintained a viral load over 100,000 copies/ml between 100 and 300 days after infection, and 19% between 200 and 400 days after infection. Extrapolating the viral decay curve led to an estimate that 16% of patients would maintain such a consistently high viral load for at least 900 days post-infection. Three people (3.4%) maintained a viral load of over one million between days 100 and 300 post-infection.

Patients with viral loads over 100,000 experienced dramatically faster falls in their CD4 count. Their CD4 counts had fallen to below 350 cells/mm3, the threshold at which the World Health Organization recommends treatment, less than three months after infection compared with nearly two years for other patients, and to 200 cells/mm3 one year after infection, compared with three years for other patients.

This is not the first study either to quantify the proportion of patients with high viral loads or to find that their CD4 counts declined faster. Another study from New York (Laraque) found that 7% of patients in New York had at least two consecutive viral loads over 100,000 copies/ml between 2007 and 2009, in a population where 53% had undetectable viral loads.

But this is one of the first longitudinal viral load studies from southern Africa, where a single subtype of HIV, subtype C, predominates. “People [with] extended high viremia....may fuel the AIDS epidemic,”comment the researchers.

Abstracts, posters and webcast

You can view the abstracts and posters from this research on the official conference website:

Abstract 508: See the abstract here and poster here.

Abstract 1024: See the abstract here and poster here.

You can also view a webcast of the themed discussion Community Viral Load on the official conference website, including the speaker Fabienne Laraque.

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References

Novitsky V et al. Extended Acutes: A Substantial Fraction of Individuals Maintain High HIV-1 RNA Levels for an Extended Time during Primary HIV-1 Subtype C Infection. Eighteenth Conference on Retroviruses and Opportunistic Infections, Boston, abstract 508, 2011. 

Laraque F et al. Disparities in Community Viral Load among HIV-infected Persons in New York City. Eighteenth Conference on Retroviruses and Opportunistic Infections, Boston, abstract 1024, 2011.