The earliest well-documented case of HIV in a human dates back to 1959 in the Congo. The earliest retrospectively described case of AIDS is believed to have been in Norway beginning in 1966. In July 1960, in the wake of Congo's independence, the United Nations recruited Francophone experts and technicians from all over the world to assist in filling administrative gaps left by Belgium, who did not leave behind an African elite to run the country. By 1962, Haitians made up the second-largest group of well-educated experts (out of the 48 national groups recruited), that totaled around 4500 in the country. Dr. Jacques Pépin, a Quebecer author of "The Origins of AIDS", stipulates that Haiti was one of HIV's entry points to the United States and that one of them may have carried HIV back across the Atlantic in the 1960s. Although the virus may have been present in the United States as early as 1966, the vast majority of infections occurring outside sub-Saharan Africa (including the U.S.) can be traced back to a single unknown individual who became infected with HIV in Haiti and then brought the infection to the United States at some time around 1969. The epidemic then rapidly spread among high-risk groups (initially, sexually promiscuous men who have sex with men). By 1978, the prevalence of HIV-1 among gay male residents of New York City and San Francisco was estimated at 5%, suggesting that several thousand individuals in the country had been infected.