HIV opportunistic infections

What it is

In HIV the organisms that cause disease change as the CD4 count falls, so the CD4 count is what tells you which organisms to consider. Above 500 the organisms are the community acquired ones, and the patient is already more likely to acquire bacterial pneumonia and to have HSV and zoster reactivation. Below 50 come cytomegalovirus, cryptococcus, Mycobacterium avium complex and primary CNS lymphoma, which is EBV associated. The infections named as the opportunistic ones are cryptococcal meningitis, toxoplasmosis, Pneumocystis pneumonia (PCP), oesophageal candidiasis, and certain cancers including Kaposi's sarcoma. They also mark the last stage: a person is diagnosed with AIDS when their CD4 cell count drops below 200 cells/mm or if they develop certain opportunistic illnesses. At that stage the viral load is high and the person is very infectious, and without treatment they typically survive about 3 yrs. The stages are three, and each carries its own CD4 band. Stage 1, acute HIV infection, is 2-4 weeks or less after infection: a flu-like illness which may last a few weeks, a large amount of virus in the blood and very contagious, and the person is often unaware because they may not feel sick right away or at all; the CD4 count is above 500/uL, and the diagnosis of acute infection needs either an Ag/Ab test or a nucleic acid test. Stage 2 is clinical latency, that is HIV inactivity or dormancy: the virus is still active but reproduces at very low levels, the phase can last a decade or longer without medicine and several decades on ART, HIV can still be transmitted during it, and the CD4 count runs 200-400/uL; at the end of this phase the viral load starts to go up and the CD4 count begins to go down. Stage 3 is AIDS, below 200/uL.