WHY ARE WOMEN IN AFRICA MORE LIKELY TO GET AIDS THAN WOMEN ELSEWHERE? “The Norwegian team believes that African women are more vulnerable to H.I.V. because of a chronic, undiagnosed parasitic disease: genital schistosomiasis (pronounced shis-to-so-MY-a-sis), often nicknamed ‘schisto.’ The disease, also known as bilharzia and snail fever, is caused by parasitic worms picked up in infested river water. It is marked by fragile sores in the far reaches of the vaginal canal that may serve as entry points for H.I.V., the virus that causes AIDS. Dr. Eyrun F. Kjetland, who leads the Otimati team, says that it is more common than syphilis or herpes, which can also open the way for H.I.V.”