The outbreak has been traced, tentatively, to three children who ate a bat, the W.H.O. said, and known threats like Ebola and Marburg have been ruled out.

A rapidly spreading unknown illness has killed 53 people in Congo, with preliminary investigations linking the outbreak to children who ate bat meat in January.

More than 50 people have died in two clusters of unknown illnesses in northwest Democratic Republic of Congo, global health authorities said.