What is Viral Load?

A person’s viral load (VL) is how much of a given virus they have in a certain quantity of a bodily fluid. Different viruses use different metrics to measure a viral load, but one of the most common is that used to measure viruses in blood, which is measured as copies of the virus in a milliliter of plasma. The VL is used to give a quick understanding of how severe a viral infection is, although the severity will in most cases be impacted by other factors as well, including a person’s immune system, and the severity of the viral strain.

Although many viruses are tested for, most commonly one’s viral load is determined in regard to hepatitis B and C, HIV-1, and cytomegalovirus. Of these, the HIV-1 viral load test is the most common, and is an important part of managing living with the disease. There are currently three tests approved for use in the United States: NucliSens HIV-1 QT, Amplicor HIV-1, and Versant/Quantiplex HIV-1 RNA.

Generally, viral load testing is used to track a patient who is already known to have been infected with a disease such as HIV-1. These tests allow doctors to see how well a patient is responding to an anti-HIV regimen, allowing them to better tailor the drugs used to inhibit the disease as much as possible. Successful therapies will see a drastic decrease in VL, between 1/30 and 1/100, within a month and a half. Within six months viral detection should be more or less impossible. Testing can also show when a patient is carrying an especially high viral load, during which time they are especially open to being infected with secondary illnesses that can be life threatening.

Although the currently-approved forms of viral load testing are too cost prohibitive to be used as modes of detection, there are some techniques used outside of the USA to detect HIV-1 which are much more affordable. VL testing for HIV is superior to antibody testing in a number of ways. It is also necessary when attempting to detect HIV in a newborn child of an HIV-positive mother, as her antibodies will still be present in the child, and therefore cannot be used to positively confirm or eliminate the presence of the virus.

Viral load testing for HIV also allows for much earlier detection than antibody testing, as antibodies may take weeks to appear in the system. Since it is during this early phase that HIV is most transmittable, being able to detect it early on could have enormous positive benefits on preventing the spread of HIV. Because of this, many public health agencies are pursuing cheap and easy-to-administer VL tests, which may be used throughout the world as an early detection system.