UNDATED ? JUNE 5: In this Centers for Disease Control and Prevention handout graphic, symptoms of one of the first known cases of the monkeypox virus are shown on a patient?s hand June 5, 2003. The CDC said the viral disease monkeypox, thought to be spread by prairie dogs, has been detected in the Americas for the first time with about 20 cases reported in Wisconsin, Illinois, and Indiana. (Photo Courtesy of CDC/Getty Images)

LONDON (AP) — A doctor who chairs a World Health Organization expert group has described the unprecedented outbreak of the rare disease monkeypox in developed countries as “a random event” that might be explained by risky sexual behavior at two recent mass events in Europe. In an interview with the Associated Press, Dr. David Heymann, said the leading theory to explain the more than 90 cases of monkeypox in a dozen countries including Britain, Spain, Switzerland, France, the U.S. and Australia was sexual transmission among gay and bisexual men at two raves held in Spain and Belgium.