In his address, titled "The Resurgent Global HIV Epidemic among MSM," Dr. Fenton said that while homosexual men everywhere have higher rates of HIV than in the general population, contrary to popular opinion MSM in wealthier countries have a vastly higher rate of infection than residents even of poorer countries.

"It is estimated that the HIV rate in MSM is eight times that of the general population in low-income countries, and 23 times the general-population rate in high-income countries," Dr. Fenton said.

"The most reliable prevalence figures suggest that, regionally, Latin America and the Caribbean have especially high rates, but in no country of the world is HIV prevalence lower in MSM than in the population as a whole. Even in South Africa, the country with more people living with HIV than any other, HIV is twice as common in MSM as it is in other people."

Dr. Fenton noted with some bewilderment that statistics show that, in the developed world, the US has the highest rate of new infections, the UK has highest overall number of infected men, and several central European countries have the highest rate of increase in numbers of infected men.

Dr. Fenton laid the blame for the MSM HIV epidemic squarely on the two most obvious characteristics of homosexual sex: anal intercourse and promiscuity.

"HIV was especially high partly for biological reasons," Fenton explained. "It is now estimated that anal sex is 18 times better at transmitting HIV than vaginal sex. The chance of HIV being caught from having receptive anal sex once with a partner with a detectable HIV viral load is about 1.4% or one in 71 encounters; but because people have sex together more than once, the per-partner likelihood of catching HIV from a sero-different partner is, in gay men, about 40%."

"Another factor in gay men's higher HIV prevalence," Fenton said, "is that because gay men have more partners and higher changeover rates, their sexual networks are more closely connected: 25% of gay men diagnosed with HIV were members of a cluster that had HIV viruses that were genetically identical, suggesting rapid transmission within the network, compared with 5% of heterosexual people."

Dr. Fenton also identified psychosocial and substance addiction elements in the exploding rates of HIV infection in MSM.

"The rates of smoking (at 27 to 66%, according to area), recreational drug use, lifetime depression (about 40%) and lifetime severe anxiety (at 20%) are all roughly double in gay men what they are in the general population," Fenton said, adding that MSM also have higher rates of traumatic experience such as child sexual abuse (CSA) and intimate partner violence (IPV) than the general population.

"In several studies that looked at rates of depression, drug use, CSA and IPV in gay men, and related them to HIV prevalence and high risk sex, gay men with three or four of these conditions were twice as likely to have HIV and three times as likely to have had recent high-risk sex than men with none of them," Dr. Fenton said.

Despite the widespread acceptance of homosexuality in high-income countries, and the incongruous statistic that in the developed world the US has the highest rate of new HIV infections, Dr. Fenton concluded that "MSM continue to be excluded, sometimes systematically, from HIV prevention, services and research because of stigma, discrimination, and criminalisation."

Professor Fenton's presentation at the British HIV Association's Autumn Conference held 14-15 November 2013 at the Queen Elizabeth II Conference Centre in London is available here.