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The prospect of a blip—a temporary spike in your viral load—may sound troubling to a person on HIV treatment or their partners, but it needn’t be.

By Bob Leahy

Blips are uncommon. They’re also unpredictable: They can occur even when you have been adherent and treatment is working well. If your viral load suddenly becomes detectable, though, don’t panic! Blips can occur if you are experiencing a brief illness such as a cold or flu at the time of your viral load test. They can even happen following a vaccination or severe allergies. If you have a detectable viral load result, your doctor may want to order a second viral load test. This is to make sure that the treatment you are on is still effective. If the next test shows you are back in the undetectable viral load range, you have experienced a blip, and there’s nothing to worry about. (If your viral load is raised on two or more tests in a row, it may be time for you and your doctor to discuss other treatment options.)

How do blips affect the risk of transmitting HIV? If your viral load has spiked above the undetectable level, don’t assume you are capable of sexually transmitting the virus to others, or that U=U no longer applies to you. This may sound odd, but it’s important to know that the research on which U=U was based used different thresholds for “undetectable.” These studies (HPTN052, PARTNER and Opposites Attract) used a detection value of below 200 copies of the virus per millilitre (ml) of blood to define an undetectable viral load. In Canada, viral load testing is capable of detecting virus in your blood at levels as low as 20 copies per ml. However, an undetectable viral load is usually defined as below 40 or 50 copies per ml.

Why is this important? Let’s assume your viral load was previously undetectable, but your latest test shows a viral load of 150. That is technically “detectable” but falls well within the definition of undetectable used by research supporting U=U. Viral load results higher than 200 copies may even mean it’s still not possible for you to transmit the virus to your sexual partners. We just don’t know the upper limit for this. What we do know with certainty is that if your viral load is below 200, you “can’t pass it on.”

Bob Leahy has been living with HIV for over 25 years and has been on treatment since 1996. He has never experienced a blip.