Acute seroconversion illness versus advanced HIV immunodeficiency
In untreated HIV, many people have a short flu-like illness around seroconversion (when antibodies first appear), then, usually after years, HIV-related illnesses as immunity weakens.
Remember
Short-lived flu-like symptoms and a rash suggest acute seroconversion, whereas recurrent oral candidiasis (thrush, a fungal infection of the mouth) suggests that loss of CD4 T cells, the white blood cells that coordinate the immune response, is weakening the immune system.
Untreated HIV passes through recognisable phases, and the pattern over time is the clue.
Acute seroconversion comes first. In many people, typically two to six weeks after infection, the virus multiplies rapidly and the immune system responds strongly, causing a short flu-like illness with a rash, fever, sore throat, tiredness, muscle aches and swollen glands. It settles by itself. It is easily mistaken for another viral illness, so offer an HIV test and ask about sexual risk.
Next comes a long, often silent latent period, with few or no symptoms, often for years. The virus keeps multiplying and the CD4 count falls slowly. The CD4 count may dip during the first illness, but its lowest point comes much later.
HIV-related illnesses appear as immunity weakens, although oral candidiasis can occur before the CD4 count falls below 200 cells/µL. Falling CD4 numbers weaken cell-mediated immunity (the arm of the immune system run by T cells), so opportunistic infections (infections that rarely harm people with healthy immunity) and recurrent or severe infections can take hold. Oral candidiasis is a classic example, and it tends to recur if the immune system stays weak. Without treatment, it usually takes years for immunity to become badly weakened.
HIV itself has no specific physical sign. The signs seen in later disease come from the immunodeficiency it causes.
Key facts
- Acute illness timing
- it usually begins about 2 to 6 weeks after infection and goes on for anything from a few days to several weeks.
- Typical early features
- a rash, fever, sore throat, tiredness, muscle aches and swollen glands.
- Quiet phase
- few or no symptoms, often for years, while CD4 T cells slowly fall.
- Later phase
- recurrent or severe infections such as oral candidiasis appear as the CD4 count falls, especially below about 200 cells/µL.
- Thrush as a warning
- oral candidiasis can occur before the CD4 count falls below 200 cells/µL, so it is a warning that the count is falling, and a CD4 count should be measured.
- Early testing
- a negative test very soon after exposure can be falsely reassuring because of the window period, the time after exposure before a test can detect infection.
Exam traps
- Persistent opportunistic infections do not happen within weeks of exposure in typical HIV: they need a low CD4 count, and that takes years.
- Thrush in HIV is not the virus killing the cells lining the mouth: HIV mainly infects immune cells that carry the CD4 receptor, and thrush develops because the immune system has lost control of Candida.
- A fever and rash within weeks of a sexual exposure can be mistaken for a bacterial sexually transmitted infection such as syphilis, but syphilis usually begins with a painless ulcer after three weeks or more, and its rash and flu-like symptoms come later.
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