New research has challenged the long-standing belief that HIV and AIDS in Africa primarily affect heterosexuals. A study published on the website of the British medical journal Lancet found that men who have sex with other men are up to 10 times more likely than their heterosexual counterparts to be infected with the virus — which suggests that the fight against AIDS on the continent may be undermined by widespread homophobia.

Researchers from Oxford University, the Population Council of Ghana and the Kenya Medical Research Institute reviewed AIDS studies conducted over the past few years and concluded that male-male sex was a major blind spot in AIDS research and policy in Africa.

Men having sex with other men is far more common in Africa than is socially acknowledged, owing to widespread hostility toward homosexuality, and the phenomenon there is underreported in research and largely ignored in public-health responses to the pandemic.

The researchers compiled statistics from a small but growing number of studies conducted in various African countries in recent years that included estimates of HIV prevalence among men who have sex with other men
Many of Africa’s gay communities operate largely underground. Zimbabwean President Robert Mugabe set the tone of the public discourse on homosexuality throughout much of the continent back in 1995, when he remarked at the Harare Book Fair that he found it "repugnant” that "... homosexuals, who offend both against the law of nature and the morals of religious beliefs espoused by our society, should have any advocates in our midst and even elsewhere in the world.”

Male-male sex is a criminal offense in some 31 sub-Saharan African countries; it even draws the death penalty in a few — on the books, at least, if hardly ever in practice. In January 2009, gay-rights activists were shocked when a Senegalese judge sentenced nine gay members of an HIV/AIDS awareness group to eight-year jail terms for "indecent conduct and unnatural acts
The sentences were subsequently overturned, but the case highlights one reason it has been so difficult to reach gay men with AIDS-prevention messages: most of them don’t want to be found. One consequence of the enforced invisibility of gays, the report concluded, is that many African men live double lives in which they are far likelier to engage in risky sexual behaviors with other men, raising the danger of further spreading the virus in their heterosexual relationships.

"In countries that protect sexual minorities, those groups are able to access services and reduce their risks,” the lead researcher, Adrian Smith, tells TIME.

"But as long as behaviors remain criminalized and stigmatized, you’re on the one hand asking a group to identify themselves and be integrated into a health system — but then the state still poses structural obstacles to prevent them doing that.”

In Uganda, whose government is considering a law to criminalize the distribution of literature with homosexual content, gays are often the targets of fire-and-brimstone sermons and public rallies.

Ugandan activists say that if the law is passed, it would prevent them from educating people about safe sexual behaviors — another issue highlighted in the report.

The report found that gay men are more likely than heterosexuals to engage in risky behaviors, perhaps because AIDS-prevention messages are aimed at heterosexuals.

"There are many men in Africa who think that anal sex is safe, because they have never been told that it’s not,” says Smith.

While activists in some countries say that attacks against gays are becoming increasingly widespread and vociferous, gays are also beginning to speak out with greater determination.

Gay-rights activists in Botswana, for example, have been fighting a loud and public battle to decriminalize homosexuality an offense now punishable by up to seven years in prison.

Increasingly, activists are targeting anti-gay laws as an obstacle to combating HIV/AIDS, according to reports from MASK, a gay-and-lesbian-advocacy group based in South Africa.

In most African countries, however, public opinion remains intolerant of homosexuality. Far more devastating than the laws, it is often the hostile attitudes of churches, families and communities that keep most gays in the closet, Smith says. "How do you access a population that doesn’t want to be found?” he says.

"That is the long-term question.”

It is a problem growingly recognized by international AIDS groups and even sometimes by national governments. Senegal may have been among the more intolerant African countries by measure of social and legal tolerance of homosexuality, but it is ironically also one of the few to offer a national HIV program that specifically addresses male-male sex.

TIME