Human immunodeficiency virus (HIV) is an infection that attacks the body’s immune system, specifically the white blood cells called CD4 cells. HIV destroys these CD4 cells, weakening a person’s immunity against opportunistic infections, such as tuberculosis and fungal infections, severe bacterial infections and some cancers.
WHO recommends that every person who may be at risk of HIV should access testing. HIV infection can be diagnosed using simple and affordable rapid diagnostic tests, as well as self-tests. It is important that HIV testing services follow the 5Cs: consent, confidentiality, counselling, correct results and connection with treatment and other services.
People diagnosed with HIV should be offered and linked to antiretroviral treatment (ART) as soon as possible following diagnosis and periodically monitored using clinical and laboratory parameters, including the test to measure virus in the blood (viral load). If ART is taken consistently, this treatment also prevents HIV transmission to others.
At diagnosis or soon after starting ART, a CD4 cell count should be checked to assess a person’s immune status. The CD4 cell count is a blood test used to assess progression of HIV disease, including risk for developing opportunistic infections and guides the use of preventive treatment. The normal range of CD4 count is from 500 to 1500 cells/mm3 of blood, and it progressively decreases over time in persons who are not receiving or not responding well to ART. If the person’s CD4 cell count falls below 200, their immunity is severely compromised, leaving them susceptible to infections and death. Someone with a CD4 count below 200 is described as having an advanced HIV disease (AHD).
HIV viral load measures the amount of virus in the blood. This test is used to monitor the level of viral replication and effectiveness of ART. The treatment goal is to reduce the viral load in the blood to undetectable levels (less than 50 copies/ml), and the persistent presence of detectable viral load (greater than 1000 copies/ml) in people living with HIV on ART is an indicator of inadequate treatment response and the need to change or adjust the treatment regimen.