Undetectable But Infectious?
posted: 10/02/2009
One of the hottest topics over the last twelve months has been the infectiousness (or otherwise) of people taking HIV treatment who have an undetectable viral load in their blood.
The debate was kick-started a year ago by what’s come to be known as the “Swiss Statement”. This said that individuals taking HIV treatment who had an undetectable viral load and no sexually transmitted infections were essentially non-infectious to their partner in a monogamous heterosexual relationship.
The authors of the Swiss Statement noted that effective HIV treatment suppressed viral load to undetectable levels in both blood and semen.
However, two studies presented to the CROI Conference in Montreal, Canada, have confirmed that HIV can be undetectable in blood, but still detectable in semen in a minority of men, even without any STIs.
1 in 7 "undetectable" men have detectable and infectious semen
A Canadian study involving 25 men found that undetectable viral load in the blood, was found with detectable virus in about 1 in 7 semen samples. The virus in semen was potentially infectious.
Semen virus sometimes blips and becomes detectable
The study also showed that viral load in semen occasionally “blipped” to detectable levels.
About a third of men who’d been taking long-term HIV treatment that suppressed viral load to undetectable levels in the blood occasionally had detectable HIV in their semen.
A larger French study looked at paired blood and semen samples from 145 men taking HIV treatment. Viral load was undetectable in 85% of these paired samples. But in 3% of samples, HIV was undetectable in blood and detectable in semen – viral load in these samples ranged between 250 and 1200 copies/ml.
Most of these detectable samples were “blips”, and the French researchers found good levels of anti-HIV drugs in the patients’ semen.
There was discussion about the implications of these findings, in particular if the levels of HIV found in semen involved a significant risk of HIV transmission. There was only one case of HIV transmission in the French study, but this involved a patient who wasn’t taking his treatment properly.
Swiss should not claim undetectable people can never transmit
However, both sets of researchers concluded that an undetectable viral load in blood doesn’t always mean that viral load is undetectable in semen, and that successful HIV treatment doesn’t entirely eliminate the risk of HIV transmission. So the Swiss statement was a bit too dogmatic - transmission is possible but seems really unlikely.
You can sign up for NAM's CROI conference dailiy update here
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