Bartusiak, Marcia F., Burke, Barbara, Chaikin, Andrew, Greenwood, Addison, Heppenheimer, T.A., Hoffman, Michelle, Holzman, David, Maggio, Elizabeth J., Moffat, Anne Simon. "3 AIDS: Solving the Molecular Puzzle." A Positron Named Priscilla: Scientific Discovery at the Frontier. Washington, DC: The National Academies Press, 1994.
Recipient of blood transfusion, blood components or tissue
Other risk, not identified
*Pattern II transmission is observed in areas of sub-Saharan Africa and in some Caribbean countries. In these countries, most of the reported cases occur in heterosexuals, and the male-to-female ratio is approximately 1 to 1. Injecting drug use and homosexual transmission either do not occur or occur rarely.
SOURCE: Centers for Disease Control, July 1993.
large numbers of free virus particles in the bloodstream. A month later the number of particles in the blood is on the decline. As the virus becomes less detectable in the blood, the protective components of the immune system become more evident, indicating that the immune system may be effectively keeping the virus at bay. Large amounts of antibodies and killer T-cells are specifically deployed to fight free virus and virally infected cells. In fact, these are the antibodies detected by standard blood tests that determine a person's HIV status. Individuals in whom antibodies are detected are said to be seropositive—that is, their blood serum tests positive for the presence of HIV. The absence of HIV in the blood means an individual is seronegative.
Following these initial events, the flu-like illness abates, and the seropositive individual enters a phase during which no obvious manifestations of infection or disease symptoms are evident. This period lasts, on average, from 8 to 10 years and is referred to as the asymptomatic phase. For a long time scientists believed that viral genes were not being