The Economist explains

Why has polio returned to London and New York?

A strain derived from the oral vaccine has gained dangerous mutations

An iron lung, sponsored by the March of Dimes charity, helps a young boy with polio to breathe, USA, circa 1955. (Photo by Kirn Vintage Stock/Corbis via Getty Images)

POLIOMYELITIS (OR POLIO, for short) terrorised America and Europe until the 1960s. It paralysed more than 15,000 people a year in America and 8,000 in Britain, mostly children. There is no treatment for polio and 5-10% of paralytic cases are fatal. The invention of a vaccine set the world on a path to eradication. The Americas region was declared free of the wild poliovirus in 1994. Europe followed in 2002 and Africa in 2020. But in June a 20-year old man was paralysed by polio in a suburb of New York City. It was America’s first confirmed case of local transmission since 1979. In recent months poliovirus has turned up in wastewater samples in London and New York in quantities that suggest the virus is circulating there. Why has polio returned?

This article appeared in the The Economist explains section of the print edition under the headline “Why has polio returned to London and New York?”

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