Disease trackers are increasingly worried that cases of polio outside of New York City could mushroom into a wider problem.
A case was identified last month in Rockland County, New York, and the virus has been detected in sewage in Rockland County, neighboring Orange County and overseas in London.
Dr. Jose Romero, director of the CDC’s National Center for Immunization and Respiratory Diseases, said many people who get polio don’t show symptoms, so it could be spreading silently.
“There are a number of individuals in the community that have been infected with poliovirus. They are shedding the virus,” he told CNN.