In the first study of its kind in a region where homosexuality and bisexuality are taboo, researchers from Weill Cornell Medical College in Qatar found evidence for concentrated HIV epidemics -- where infection rates are above 5 percent in a certain population group -- in several countries such as Egypt, Sudan, Pakistan and Tunisia.
In one setting in Pakistan, HIV rates reached up to 28 percent, they said in a study in the Public Library of Science (PLoS) Medicine journal.
The researchers stressed the need for at-risk countries to act quickly to expand HIV surveillance and access to HIV testing, prevention and treatment services for men who have sex with men in an effort to halt further spread.
An estimated 33.3 million people worldwide had the human immunodeficiency virus (HIV) that causes AIDS in 2009, according to the latest United Nations data, and 22.5 million of those live in sub-Saharan Africa.
There is little published data on the Middle East and North African regions and Ghina Mumtaz, who led the study with colleague Laith Abu-Raddad, said this had been driving misconceptions that there is no reliable information at all.
But when they looked more closely, the researchers found that data was indeed available, although often it had been gathered by various groups and not made public.
After analysing various reports, they found "considerable and increasing epidemiological evidence on HIV and risk behavior among men who have sex with men" in the region.
The findings were worrying, but not surprising, the researchers said. They found that by 2008, HIV transmission via anal sex among men was responsible for more than a quarter of notified cases of HIV in several countries in the region.
He added that more testing, surveillance and access to HIV services would help limit the size of the epidemics and prevent HIV transmission from reaching other population groups such as women and heterosexuals. He stressed that this did not have to require uncomfortable public statements by governments.
Morocco, Lebanon and Pakistan have supported NGOs to deliver services to this highly hidden population without any direct government involvement, Mumtaz added.