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176 SEcTioN ii Microbiology ` microbiology—Virology Microbiology ` microbiology—Virology

Time course of untreated HIV infection
Window period +/– Acute HIV infection Skin and mucous Systemic immuno-
Viral dissemination membrane deficiency/AIDS-
Seeding of lymphoid organs Clinical latency infections defining illnesses

1200 Anti-envelope antibody (gp120) 10 7
1100 Death

1000
CD8+ T cell
900
CD4+ or CD8+ cells/mm 3 700 CD4+ T cell HIV RNA copies/mL
800

600

500
HIV RNA
400 10 4
300
200 10 3

100
Primary
infection 0 10 2
0 1 2 3 1 2 3 4 5 6 7 8 9 10 11
Months Years
Dashed lines on CD4+ count axis indicate moderate immunocompromise Four stages of untreated infection:
3
(< 400 CD4+ cells/mm ) and when AIDS-defining illnesses emerge (< 200 1. Flu-like (acute)
3
CD4+ cells/mm ). 2. Feeling fine (latent)
Most patients who do not receive treatment eventually die of complications of 3. Falling count
HIV infection. 4. Final crisis
During clinical latency phase, virus replicates
in lymph nodes

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