vaccine-derived polio

When public health specialists look at the annual case counts, some see a trend that raises questions about how realistic the goal of a polio-free world might be.

Scientists in Britain have detected multiple versions of the virus in wastewater. Officials say the risk to the public is extremely low and urge people to ensure their polio vaccines are up to date.

The Kick Polio Out of Africa Campaign began in 1996. This week, the World Health Organization announced that wild polio has been eradicated — although there is a caveat.

Health officials have long known that virus from the oral vaccine can contaminate water supplies; they underestimated how big a problem this would be.