Immunodeficiency is a weakened immune defense — and it comes in two forms. Some people are born with a defect; far more acquire one later in life. The most important acquired cause is HIV, which slowly destroys CD4 T cells. Explore both, then drag the HIV timeline.
Pick a kind
Where does the defect come from?tap Primary or Secondary
Root cause
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Typical onset
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How common
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Two routes to the same problemWhichever the route, the result is the same: the body can no longer defend itself, so ordinary microbes cause serious infections. Tap each kind to see the difference.
CD4 T cells over time (untreated HIV)
Year 0.0 · CD4 900 cells/µLAcute
CD4 countHIV viral load (relative)
The natural history of HIVdrag the slider to begin