Polio is not expected to spread widely in the U.S. due to the high rate of vaccinations, experts say.
Their comments came in interviews with Axios. The poliovirus was detected in wastewater samples in New York state and London.
News of the resurgence of the virus came as the U.S. is still dealing with COVID-19 and an outbreak of monkeypox.
About 93% of children in the U.S. receive vaccinations against polio by the time they turn two, the CDC reported.
Aaron Glatt, the infectious disease chief at Mount Sinai South Nassau in New York, and other experts told Axios that those up to date on their polio vaccines have little to worry about.
"If you're an unvaccinated person living in Rockland or Orange County [New York], where sewage is showing there's polio in it, I would be concerned and get vaccinated," he said.
Patricia Jackson, a spokeswoman for the Association for Professionals in Infection Control and Epidemiology and director of infection prevention White Rock Medical Center in Dallas, added: "The good news about this is, if you're vaccinated, you're protected.”
New York State Health Commissioner Mary Bassett on Friday had 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.