The governor of New York has declared a state of emergency over polio as evidence emerges that the virus is spreading across the state.
Health officials say wastewater samples in New York City and four adjacent counties have tested positive for a poliovirus that can cause paralysis. Although only one case has so far been confirmed, it was the first in the country in nearly a decade.
Polio was largely eradicated from the US by vaccinations that began in 1955. By 1979, the US was declared polio-free. But according to New York officials, vaccination rates are too low in parts of the state. Friday's emergency declaration is aimed at boosting flagging immunisation rates.
There is no cure for polio, but it can be prevented by the vaccine. Mostly affecting children, the virus typically causes muscle weakness and paralysis, and in the most serious cases permanent disability and death.
New York's state health department said it aims to boost vaccination rates from the current state-wide average of about 79% to above 90%.