Four African countries have reported new cases of polio linked to the oral vaccine, as global health numbers show there are now more children being paralyzed by viruses originating in vaccines than in the wild.

After a devastating cyclone in Mozambique, a cholera outbreak has been declared in the regional city of Beira, many of whose half-million residents live in slums, and in a few outlying communities where scores of thousands of people now huddle in displacement camps with few toilets and little clean water.