New York State Health Commissioner Mary Bassett on Friday warned of a potential polio outbreak in the city after an adult in the metro area tested positive for the virus.
"Based on earlier polio outbreaks, New Yorkers should know that for every one case of paralytic polio observed, there may be hundreds of other people infected," Bassett said.
"Coupled with the latest wastewater findings, the department is treating the single case of polio as just the tip of the iceberg of much greater potential spread."
Bassett urged residents to get vaccinated.
"As we learn more, what we do know is clear: the danger of polio is present in New York today. We must meet this moment by ensuring that adults, including pregnant people, and young children by two months of age are up to date with their immunization — the safe protection against this debilitating virus that every New Yorker needs."
The polio virus has now been found in seven different wastewater samples in two adjacent counties north of New York City, health officials said.
Polio, once one of the nation's most feared diseases, was declared eliminated in the United States in 1979, more than two decades after vaccines became available.
A majority of people infected with polio have no symptoms but can still shed the virus and give it to others for days or weeks. A small percentage of people who get the disease suffer paralysis. The disease is fatal for between 5-10% of those paralyzed.
The man who caught polio was hospitalized with paralysis last month.
All school children in New York are required to have a polio vaccine, but enforcement of vaccination rules in some areas can be lax. Rockland and Orange counties are both known as centers of vaccine resistance. Statewide, about 79% of children have completed their polio vaccination series by age two. In Orange County, that rate is 59%. In Rockland it is 60%.
Information from the Associated Press was used in this report.