Getting the Low-Down on Viral Loads

At the heart of the U=U message is the concept of “undetectable” — the point at which an individual’s viral load is so low, they cannot transmit the virus to sexual partners. But what is a viral load, and how is it determined?

We asked Dr. Sebastian Ruhs, director of Chase Brexton Health Care’s Infectious Disease Center of Excellence, to explain the concept of viral load, how it’s determined, and how an individual can lower their count.

Dr. Sebastian Ruhs, Chase Brexton Health Care

What is a “viral load”?

A viral load is the number of viruses that are found in one milliliter of blood. This number helps us to get an idea of either how active a HIV infection is, or how well controlled it is on medication. A person’s viral load can be anywhere from undetectable to millions of copies. Most people who are not on medication have a viral load of less than 100,000 copies per milliliter. The higher the number, the faster the progression of the disease—the lower the number, the better.

How is an individual’s viral load determined?

To determine someone’s viral load, their blood needs to be sent to a specialty lab. Modern technology allows us to precisely count the amount of virus in each milliliter of blood. It usually takes two to four days to get those results back.

How is someone’s viral load reduced?

The only way of reliably reducing someone’s viral load is by taking HIV medication daily. Those meds stop the virus from replicating. Meaning, the virus is put into an inactive or dormant stage.

At what point is someone’s viral load considered undetectable?

There are three layers to this question.

First, completely undetectable means there is absolutely no virus found in the blood.

Second, current technology can count as low as 20 viral copies per milliliter. Anything below 20 copies cannot be counted and will be reported as less than 20 copies detected. Since 20 copies is an extremely low count without any clinical implication, most experts will call this “undetectable” as well.

Finally, if the count is between 20 and 200 copies, we do not talk about “undetectable” at that point. However, for most clinical purposes, anything less than 200 copies per milliliter is considered a treatment success. This also ties into the research behind the U=U campaign, which has identified that anyone with less than 200 copies per milliliter cannot sexually transmit the virus. Any viral load over 200 copies is generally concerning and requires further attention. 

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