Here are the basics: In simple terms, “viral load” is a number doctors use to describe the amount of HIV in the blood. The more HIV there is in your blood, the higher your viral load will be. Conversely, if there are very low amounts of HIV in your blood, then you’re described as being undetectable.
Viral loads can go up or down depending on other factors, such as having a sexually transmitted infection, or getting a flu vaccine (but this is temporary).
What’s key is that once you’re diagnosed as being HIV positive, you talk with your doctor about when you should start treatment. Doctors suggest people with HIV start treatment immediately following their diagnosis.
Generally, when you begin HIV treatment, your viral load falls. Health experts agree that taking antiretroviral drugs (ARVs) is very important for both your health and for reducing your risk of passing HIV to sex partners.
In fact, studies with HIV-positive people found that when they took their meds each day as prescribed, this made it almost impossible for them to pass the virus on to their sexual partners.
But just because the viral load in your blood is low doesn’t mean the viral load in other bodily fluids is also down and undetectable. “Keep in mind that a viral load test measures the amount of HIV virus in your blood. But sexual partners are usually infected by virus in sexual fluids, such as semen or vaginal or anal secretions,” says Susa Coffey, MD, a doctor at the U.S. Department of Veterans Affairs.
“Unfortunately, the viral load in these fluids can be high even when the viral load in blood is low,” Coffey continues. “And factors like STIs [sexually transmitted infections] can increase the risk of HIV transmission.”
So while being undetectable greatly lowers the risk of HIV transmission, there is still some risk. For the best outcome, Coffey says, it’s important to ask your health care provider for advice that’s specific to you and to your partner.
And remember, for ARV therapy to keep HIV suppressed to undetectable levels, it’s key you take your meds every day as prescribed.