Ratodero (Pakistan): Nothing seemed unusual to Rehmana Bibi, the mother of 10-year-old Ali Raza, when the boy came down with a fever at their home in the dusty, largely neglected district of Larkana in southern Pakistan. Bibi took her son to a local doctor, who prescribed paracetamol syrup for Raza and told her there was no need to worry.

But she panicked after being alerted that several children who initially came down with a fever had tested positive for HIV in nearby villages. Alarmed, Bibi took Raza to a hospital where medical tests confirmed the boy was among about 500 people, mostly children, who authorities say tested positive for the virus, which can lead to AIDS. A local physician who has AIDS has since been arrested and is being investigated for possibly intentionally infecting patients.