In the context of HIV disease: HIV is spread most commonly by sexual contact with an infected partner. The
virus can enter the body through the mucosal lining of the vagina, vulva, penis, rectum or, very rarely, the mouth during sex. The likelihood of transmission is increased by factors that may damage these linings, especially other sexually transmitted diseases that cause ulcers or inflammation. Studies of
SIV infection of the genital membranes of nonhuman primates suggest that the sentinel cells known as mucosal
dendritic cells may be the first cells infected. Infected
dendritic cells may migrate to
lymph nodes and infect other cells. HIV also is spread through contact with infected blood, most often by the sharing of drug needles or syringes contaminated with minute quantities of blood containing the
virus. Children can contract HIV from their infected mothers either during pregnancy or birth, or postnatally, via breastfeeding. Current research indicates that the
AIDS virus may be 100 to 1000 times more
contagious during the first two months of
infection, when routine
AIDS tests are unable to tell whether people are infected. See also
Lymph Nodes;
Simian Immunodeficiency Virus.