HIV Digest	HIV Digest Archive

It has long been hypothesized that semen viral load is the explanation for why there appears to be greater HIV transmission associated with acute infection. A study confirms this perception. People who have sex with a partner during an acute HIV infection phase may be at a 20-fold greater risk per exposure than are partners of individuals who are at a virologic set point, the study reported.

"Confirming what the natural history of semen HIV viral burden [is] has been a difficult challenge because patients who are acutely infected don't often consent to donate semen, and moreover, they're being treated," notes one researcher.

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UNC researchers worked with investigators from the University Hospital in St. Gallen, Switzerland, and Emory University in Atlanta. Together they obtained matched blood and semen concentrations from 30 patients who had acute infection. "We timed each data point for each individual from the time of their estimated infection, and what we found was that just as has been described in blood, semen HIV burden appears to be much higher in patients around the time of the onset of symptoms," said investigators. "And it decreases over time," paralleling the decrease over time found in blood, he added. "The [semen viral load] decrease is gradual over four months to the virologic set point."

After running a statistical analysis with their findings and plugging these into a previously published model, investigators were able to estimate the transmission rate per coital act probability for patients with different semen concentrations. "The partners of patients with acute infection would be at approximately 20-fold increased risk with each sexual act around the time of acute infection, compared with four months later," researchers concluded.

Editor's Note: from AIDS Alert