Why didn an epidemic occur immediately after the first known HIV infections?
“HIV did not become epidemic until 20 to 30 years later [after known infection in 1959], perhaps because of the migration of poor and young sexually active individuals from rural areas to urban centers in developing countries, with subsequent return migration and, internationally, due to civil wars, tourism, business travel and the drug trade” (NIAID citing Quinn, “Population migration and the spread of types 1 and 2 human immunodeficiency viruses,” Proc Natl Acad Sci USA 1994;91(7):2407-14.)
