HUMAN IMMUNODEFICIENCY VIRUS
HIV is the causative
agent of AIDS. The definition of AIDS, as determined by the CDC, has changed
several times since the syn-drome was first recognized in 1981. In general, the
definition sets a point in the continuum of HIV pathogenesis in which the host
has clinically demonstrated profound immune dysfunction. Many opportunistic
infections and neoplasms serve as markersfor immunosuppression severity. Since
1993, the AIDS defini-tion has also included a CD4-positive (CD4+) cell count of less than 200 as a threshold
criterion. CD4+ cells are a subset of lymphocytes and one of the
targets of HIV infection.
HIV is transmitted through sexual contact, percutaneous
in-jection of contaminated blood, or perinatally from infected mother to fetus.
Most people infected by the percutaneous route are intravenous or injecting
drug users who share contaminated needles, but transmission is also remotely
possible through con-taminated blood transfusion. Since 1985, all blood
transfusions have been screened, and transfusion-related transmission of HIV is
now extremely unlikely.
Health care workers can
be infected through the percutaneous route if needlestick or other injury from
a sharp object introduces contaminated blood. Prospective studies of this risk
demonstrate that less than 1% of such occupational exposures (in which the
source patient is infected with HIV) lead to transmission (CDC 2001a). Despite
the rarity of transmission, health care workers are advised to take extreme
care to avoid needlestick or mucous membrane exposure to blood of all patients.
Since 2001, employers in health care institutions are required to provide
devices designed to reduce the risk of needlestick and other injury when such
devices are found to be beneficial. Since 1996, the CDC has recommended
postexposure prophylaxis for significant occupa-tional exposures to HIV.
Counseling about the advisability of prophylaxis and appropriate medication and
dose selection should be made on a case-by-case basis. Table 70-5 provides the
recommended algorithm to determine which combination of antiretroviral drugs
should be offered to the exposed health care worker. All health care workers
should understand the need to re-port a needlestick or other percutaneous
exposure immediately (CDC, 2001f ).