You are here: Section 2 » 2.2 Download Full Resource PDF [2.5MB] Download PDF Version

2.2 – What do rehabilitation providers need to know about CD4 count and viral load?

CD4 count and viral load are two of the surrogate markers (clues) used to understand disease progression in HIV. These measures will help a rehabilitation provider understand a patient’s immune system at a single point in time as well as changes in immune status over time

CD4 count

Cells in a person’s body with CD4 receptors on their surface are the primary targets destroyed by HIV. 

CD4 count is the most important surrogate marker for health status and strongest predictor of disease progression.

How to interpret CD4 count:

  • A normal CD4 count level is between 500 to 1500 cells/mm3.
  • CD4 count in a healthy individual varies over time.
  • In a person living with HIV, the CD4 count will become lower as her/his HIV disease worsens.
  • Most opportunistic infections occur when a CD4 count is less than 200 cells/mm3.

The CD4 count is influenced by a number of factors (e.g., stress, illness, time at which it was measured) and therefore, the trend in CD4 counts is more important versus one test at a single point in time.

Viral load

Viral load reflects the amount of virus (HIV) within the body. Viral load is used to predict the rate of progression of HIV disease and to initiate, monitor, and change antiretroviral therapy.

How to interpret viral load levels:

  • The HIV viral load test measures the amount of HIV virus, in each ml or cubic centimeter of blood (e.g., from 50 to 500,000).
  • The higher the viral load, the more viral reproduction (HIV copying itself) is taking place, and the more active (worse) the disease.
  • Viral load tests struggle to measure fewer than 50 HIV viruses in each ml of blood and so the test may say that the viral load is "undetectable."
    • This does not mean that a person is cured of HIV.
    • An undetectable viral load means that a person’s HIV disease is well controlled (but not gone).
    • It is also important to note that it is still possible to transmit the virus when the viral load is ‘undetectable’.
    • It also does not mean that the patient should discontinue taking their treatment, unless advised by the health care team.

The goal of ART is to reduce viral load to the lowest possible level for the longest possible time.