LONDON CHILDREN OFFERED POLIO VACCINE BOOSTER

Every child in London age 1 to 9 should be offered a booster dose of polio vaccine, British health authorities said on Wednesday, after traces of the virus turned up in sewage samples across one-quarter of the city’s boroughs, though no individual cases of the disease have been reported.

Health authorities declared a national incident in June — a designation that is used to underscore the potential seriousness of the issue — after sewage samples suggested the virus was spreading in London. Now, officials said, samples indicated that it had spread beyond a close network of a few individuals.

Normally, routine surveillance of sewage in Britain picks up the virus once or twice a year, the U.K. Health Security Agency said in a statement, but between February and July, 116 samples of type 2 poliovirus were detected in samples from eight London boroughs in the north and east of the city.

“No cases of polio have been reported and for the majority of the population, who are fully vaccinated, the risk is low,” Dr. Vanessa Saliba, a consultant epidemiologist at the health agency, said in the statement.

“But we know the areas in London where the poliovirus is being transmitted have some of the lowest vaccination rates. This is why the virus is spreading in these communities and puts those residents not fully vaccinated at greater risk.”

Polio, which can cause paralysis, was once a profoundly feared childhood disease but has practically been eradicated by vaccination. Britain’s last known case was in 1984, and a case in New York last month was the first in the United States in nearly a decade.