Viral load, also known as viral burden, viral titre or viral titer, is a numerical expression of the quantity of virus in a given volume. It is often expressed as viral particles, or infectious particles per mL depending on the type of assay. A higher viral burden, titre, or viral load often correlates with the severity of an active viral infection. The quantity of virus/mL can be calculated by estimating the live amount of virus in an involved body fluid. For example, it can be given in RNA copies per millilitre of blood plasma.
Tracking viral load is used to monitor therapy during chronic viral infections, and in immunocompromised patients such as those recovering from bone marrow or solid organ transplantation. Currently, routine testing is available for HIV-1, cytomegalovirus, hepatitis B virus, and hepatitis C virus. Viral load monitoring for HIV is of particular interest in the treatment of people with HIV, as this is continually discussed in the context of management of HIV/AIDS.
Having an undetectable viral load lowers greatly the chances of transmitting the virus to the sexual and drug using partners who are HIV negative. However even when someone’s viral load is undetectable, HIV can still exist in semen, vaginal and rectal fluids breast milk and other parts of your body. For this reason, someone with undetectable viral load should continue to take steps to prevent HIV transmission. HIV may still be found in genital fluids (semen or vaginal fluids), the viral load test only measures the amount of HIV in the blood.
Although ART lowers viral load in in genital fluids even when its undetectable in the blood. The viral load may go up between tests. When this happens, the person may be more likely to transmit HIV to their partners. The viral load may go up without the person knowing it because they may not feel any different. Sexually transmitted diseases (STD’s) can increase the viral load in genital fluids. This means if someone is living with HIV and also have an STD, they may be able to transmit HIV to their partner even if their viral load is undetectable.