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 doctor, who prescribed acetaminophen syrup 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.