Page 34 - AIDSBK23C

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NATURAL HISTORY OF HIV INFECTION

On average, there is a period of 8 to 10 years from initial infection to clinical AIDS in
adults, though AIDS may be manifested in less than two years or be delayed in onset beyond 10
years.[191] About 10% of persons will rapidly progress to AIDS in 2 to 3 years following HIV
infection, while about 10% have not progressed to AIDS even after 10 years.[192] It is clear that
the longer an individual is infected, the more likely the development of illness and subsequent
death will be. Thus, HIV infection does not follow the pattern of more traditional viral diseases
in which the risk of serious illness or death decreases with time. There has been no study to date
that shows a failure of HIV-infected persons to evolve to clinical AIDS over time, though the
speed at which this evolution occurs may vary, and a small number of HIV-infected persons will
not progress to AIDS for many years.[115]
Primary HIV infection, also known as acute retroviral syndrome, may produce a mild and
self-limited disease in 50 to 90% of persons infected with HIV, regardless of the mode of
transmission. The time from mucosal infection to viremia is about 4 to 11 days. The time from
exposure to development of symptoms averages 2 to 6 weeks. The symptoms may persist for 1
to 2 weeks, after which symptoms subside over 1 to 2 months. Prospective studies of acute HIV
infections show that fever, fatigue, arthralgia or myalgia, lymphadenopathy, pharyngitis, diffuse
erythematous macular or mixed maculopapular rash (often involving the trunk), diarrhea, nausea
or vomiting, weight loss, night sweats, mucocutaneous ulcerations, and headache are the most
common symptoms seen with acute HIV infection. An acute meningoencephalitis may be seen
in some recent infections and appear as an “aseptic meningitis.” The symptoms of acute HIV
infection resemble a flu-like or an infectious mononucleosis-like syndrome. Primary HIV
infection is not life-threatening.[193,194] Primary HIV infection in children is usually
accompanied by one or more of the following: mononucleosis-like syndrome, dermatitis, or
generalized lymphadenopathy.[195]
In acute HIV infection, the peripheral blood may demonstrate lymphopenia and/or
thrombocytopenia. However, atypical lymphocytes are absent. Although the CD4 cells are
decreasing, the levels may initially remain in the normal range, but depletion continues.
Simultaneously, there is an increase in cytotoxic CD8 lymphocytes that continues as symptoms
subside and viremia decreases.[194]
During this acute phase of HIV infection, there is active viral replication, particularly in
CD4 lymphocytes, and a marked HIV viremia. This peripheral blood viremia is at least as high
as 50,000 copies/mL and often in the range of 1,000,000 to 10,000,000 copies/mL of HIV-1
RNA. High titers of cytopathic HIV are detectable in the blood so that the p24 antigen test is
usually (but not always) positive, while HIV antibody tests (such as enzyme immunoassay) are
often negative in the first three weeks. The viremia is greater in persons whose primary HIV
infection is symptomatic.[21,86,193,194]
During this viremic phase, HIV disseminates throughout the body to lymphoid tissues
and other organs such as brain. There are alterations in peripheral blood mononuclear cells
marked by a decline in CD4+ lymphocytes. Persons acutely infected with HIV are highly
infectious because of the high levels of HIV, both in blood as well as in genital secretions. Over
half of all HIV infections may be transmitted during this period.[193]
Generally, within 3 weeks to 3 months following initial infection with HIV, the immune
response is accompanied by a simultaneous decline in HIV viremia. Both humoral and cell