If you have been diagnosed with human immunodeficiency virus (HIV), initially to determine the status of the infection and subsequently to monitor the effectiveness of antiretroviral treatment
HIV Viral Load
When first diagnosed with HIV; 2 to 8 weeks after the start of therapy or therapy changes, then every 4 to 8 weeks until the viral load is not detectable; then every 3 to 4 months if you are on stable therapy and the virus remains suppressed; after two years of this, viral load testing frequency may be decreased to every 6 months.
A blood sample drawn from a vein in your arm
Human immunodeficiency virus (HIV) is the virus that can cause acquired immunodeficiency syndrome (AIDS). This test measures the amount (viral load) of HIV genetic material (RNA) in your blood.
When you are initially infected with HIV, the virus replicates — it produces more and more copies of itself. The main target of HIV is the CD4 cells, which are a type of white blood cell that fights infections. The virus enters these cells and uses them to replicate and spread throughout your body. It moves into your lymph nodes, spleen, and other parts of your body.
In the early stages of infection, there may not be any noticeable signs or symptoms of disease or only flu-like symptoms, although the virus is usually present in high amounts. Without treatment and even when there are no symptoms, the virus continues to replicate and the viral load will increase. HIV kills your CD4 cells, so the number of CD4 cells will decrease as HIV infection progresses.
About 3-8 weeks after initial exposure to the virus, your immune system begins to produce HIV antibodies in response to the infection and suppresses the HIV viral load, decreasing it to a low level. Initial symptoms typically resolve, but your infection does not go away.
The only way to determine whether you have been infected is through HIV testing. If not detected early and treated, an HIV infection may slowly degrade your immune system. After several years and without treatment, the immune system can become so weakened that the disease begins to affect your ability to fight infections and certain cancers. Symptoms of AIDS begin to appear at this stage as your body becomes more susceptible to infections with microorganisms such as tuberculosis and fungi or other diseases such as Kaposi's sarcoma.
When you are diagnosed, you are given antiretroviral treatments for HIV (also called highly active antiretroviral therapy or HAART) to suppress the amount of HIV virus present in your blood, limiting its ability to replicate and reducing the risk of progressing to AIDS. Evidence shows that keeping the viral load at undetectable levels decreases your risk of progressing to AIDS and greatly improves your long-term health. If you have HIV and discontinues treatment or if it loses its effectiveness, then your HIV viral load can begin to increase again.
The HIV RNA test detects HIV virus genetic material and measures how many copies of HIV (viral load) are present in your blood at a particular time. It can track increases and decreases in your HIV viral load and, in conjunction with a CD4 count, be used to evaluate treatment effectiveness.
- How is the test used?
The HIV viral load test is used initially, along with a CD4 count, to determine the status of your HIV infection when you have been diagnosed with the disease. The viral load is then used to monitor the effectiveness of your antiretroviral treatment (ART) over time.
The HIV viral load may also be used to help determine whether the virus infecting you has become drug-resistant. If you do not respond well to treatment and the amount of virus continues to increase, then the virus may be resistant to that particular ART. Your treatment will then likely be modified.
HIV viral load tests are most useful when they are compared with results obtained from your earlier tests. They are used in combination with the CD4 count to monitor how effective ART is in suppressing your HIV. (For more details, see the article on the CD4 Count.)
- When is it ordered?
An HIV viral load test is typically ordered with a CD4 count when you are first diagnosed with HIV infection as part of a baseline measurement. After the baseline, a viral load test will usually be ordered at intervals over time, depending on a few different factors.
The following table summarizes recommendations* for the timing of viral load testing and CD4 counts:
Your Clinical Status Viral Load CD4 Count When first diagnosed Test performed Test performed After initiating ART Within 2-4 weeks and then every 4-8 weeks until virus is suppressed (undetectable) 3 months later During the first 2 years of stable ART Every 3-4 months Every 3-6 months After 2 years of stable ART, virus undetectable, and CD4 greater than 300 cells/mm3 Can extend to every 6 months Annually; if CD4 consistently greater than 500 cells/mm3, monitoring is optional After changing ART due to side effects or simplifying drug regimen when your virus is suppressed After 4-8 weeks, to confirm drug effectiveness Monitor according to prior CD4 count and the amount of time you have been on ART, as detailed above After changing ART due to increased viral load (treatment failure) Within 2-4 weeks and then every 4-8 weeks until virus undetectable Every 3-6 months While on ART and viral load is consistently greater than 200 copies/mL Every 3 months Every 3-6 months With new HIV symptoms or start of new treatment with interferon, corticosteroids or cancer drugs Every 3 months Perform test and monitor according to health status (e.g., new HIV symptoms, opportunistic infections)
*Adapted from Guidelines for the Use of Antiretroviral Agents in HIV-1–Infected Adults and Adolescents, Table 4. Recommendations on the Indications and Frequency of Viral Load and CD4 Count Monitoring.
- What does the test result mean?
HIV viral load tests are reported as the number of HIV copies in a milliliter (copies/mL) of blood.
If your viral load measurement is high, it generally indicates that HIV is present and replicating. Initial, untreated, and uncontrolled HIV viral loads can range as high as one million or more copies/mL.
If you are receiving antiretroviral treatment (ART), a high viral load means that the treatment is not effective. If you are not responding to treatment, then it will likely be changed. You should undergo HIV drug resistance testing to help in the selection of an alternative therapy.
Viral loads that are consistently less than 200 copies/mL indicate that your virus is adequately suppressed and that the risk of disease progression is low. Nevertheless, an undetectable viral load in someone who has a diagnosed HIV infection does not mean that your HIV infection is cured. It means only that the level of your HIV RNA is currently below the threshold needed for detection by the test.
Changes in your viral load can often be more important during HIV monitoring than a single test result. An increasing viral load indicates either that your infection is getting worse or that your virus has developed resistance to the drugs that are being used for therapy and are no longer effective. A decreasing viral load indicates improvement, treatment effectiveness, and suppression of your HIV infection.
- Why does my doctor want me to go to the same laboratory each time I have my HIV viral load tested?
Laboratories may use different methods to measure HIV viral load, so results can vary from lab to lab. When you have a series of viral load tests done, it is advised that you have the tests done by the same method, typically by the same laboratory, so that the results can be compared and interpreted correctly. Tracking increases or decreases of your viral load must be done by the same method to provide an accurate picture of whether the virus is replicating or staying stable with the current therapy.
- How is HIV treated?
It is recommended that all individuals diagnosed with HIV infection receive antiretroviral treatment as soon as possible, including pregnant women. People typically take at least three drugs from two different classes in order to prevent or minimize virus replication and the emergence of drug-resistant strains. Combinations of three or more antiretroviral drugs are referred to as highly active antiretroviral therapy or HAART. (Read the HIV Infection and AIDS article for more details.)
- Will exercise, nutrition, and other lifestyle modifications help decrease my HIV viral load?
There is no direct link between HIV viral load and exercise, nutrition, or other lifestyle factors. However, the Centers for Disease Control and Prevention (CDC) does suggest that if you eat healthy foods, you will stay strong and keep up your energy. More information about this is contained in the CDC brochure Living with HIV.
- If I have undetectable HIV viral load, can I still spread the disease?
According to the Centers for Disease Control and Prevention, someone who is HIV-positive and has an undetectable viral load by taking antiretroviral treatment (ART) cannot pass the virus to an HIV-negative partner through sex. It is not known if those with undetectable viral loads can transmit the virus through syringes and other means.
- Can an HIV RNA test be used to screen for HIV?
The recommended test for HIV screening is a combination test that detects HIV antibody and HIV antigen. By detecting both antibody and antigen, the combination test increases the likelihood that an infection is detected soon after exposure. Most HIV screening tests detect only HIV antibody but are good options for screening because they may be available as rapid tests and at the point of care. If any of these screening tests are positive, they must be followed by another different antibody test. If the second test is positive, then HIV diagnosis is confirmed. If, however, the first and second result do not match, then an HIV RNA test may be done to help establish a diagnosis.
The recommended screening test for newborns, however, is an HIV RNA test (see next question).
- Why is the HIV RNA test used to test newborns for HIV infection?
Babies born to mothers infected with HIV are typically tested soon after birth (usually within one to four months) to help determine whether the mother has passed the infection to her baby. An HIV RNA test is performed in babies instead of standard screening HIV antibody tests because antibodies to HIV produced by the mother can cross the placenta and enter the baby's blood. If an HIV antibody test were to be performed on a baby, the result could be positive even though the baby is not infected with the virus.
An infant with a positive HIV RNA test is likely infected with the virus. Repeat testing done on a second blood specimen is done to confirm the diagnosis. A negative HIV RNA test means that the baby is not infected (or may have been tested too soon after birth). If negative, the test is usually repeated when the infant is older than 1 month and again when the baby is older than 4 months. This may be necessary as the amount of virus may not be at a detectable level.
- What is HIV provirus?
Even when HIV is undetectable in your blood, it persists in cells and tissues throughout the body as HIV provirus. HIV provirus refers to virus that has moved into the nucleus of cells and has become integrated with the DNA of the host cell. This is also called "HIV proviral DNA."