1 Immune system and CD4 count

1.12 CD4 count cut-offs and the risks of opportunistic infections

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An opportunistic infection (OI) is the name given to an HIV-related illness that your body would normally fight off, but that takes advantage of the damage HIV has caused to your immune system.

The lower a person's CD4 count, the higher the risk that they will develop HIV-related illnesses. This is why monitoring of CD4 levels is important when you are not on treatment.

You can still be well and healthy with a CD4 count that is below 200, below 100, below 50 or even below 10 – but it is much more likely that you will have serious health-related problems.

Different illnesses become more likely at different CD4 counts. Many serious and life threatening illnesses become a risk when the CD4 count drops to under 200 cells/mm³.

Opportunistic infections that occur at different CD4 counts

CD4 count below 300

• Diarrhoea from bacteria infections microsporidia and cryptosporidia
• Skin problems – candida (thrush), dry skin, etc

CD4 count below 200

• PCP (fungal pneumonia) and chest infections
• Toxoplasmosis – parasitic infection that can cause brain lesions

CD4 count below 100

• MAI /MAC (mycobacterium avium complex) – bacterial infections similar to TB
• Cryptococcus – fungal infection that can cause meningitis in the brain and PCP-like symptoms in the lungs

CD4 count below 50

• CMV (cytomegalovirus) – a viral infection that can cause permanent vision loss and blindness and can also affect other organs

The lower your CD4 count the higher the risk of these and other illnesses.

When your CD4 count increases after starting HIV treatment, your immune system is often able to deal with these infections by itself again.