Increased risk of death from measles in children with a sibling of opposite sex in Senegal.

OBJECTIVE To examine whether contracting measles from a sibling of the opposite sex affects mortality. DESIGN Prospective registration during 15-20 years of all births and deaths, including 243 measles related deaths. Measles infection was not registered; however, as in fatal cases measles was probably contracted from a maternal sibling the risk of dying during measles outbreaks was examined in families with two boys, two girls, or a boy and a girl. SETTING 31 small villages in two rural areas of eastern Senegal. SUBJECTS 766 children living in families with two children aged under 10 years during outbreaks of measles, 107 (14%) of whom died of measles. MAIN OUTCOME MEASURE Deaths from measles, size of village, age and sex of maternal siblings. RESULTS The interval between outbreaks in the same village was greater than 10 years. The risk of dying of measles was significantly related to age, increasing with the age difference between siblings and decreasing with the size of village. In a multiple logistic regression analysis adjusting for these background factors, children in families with a boy and a girl had a significantly higher mortality than children in families with two boys or two girls (odds ratio = 1.81, 95% confidence interval 1.17 to 2.82). The increase in risk was the same for boys and girls in families with two children one of whom was a boy and one a girl. CONCLUSION Cross sexual transmission may be an important determinant of severity of measles infection.