An official from the Centers for Disease Control and Prevention (CDC) said Thursday that a polio case detected in New York last month, the first confirmed U.S. case in nearly a decade, could very well be an indication of “several hundred cases” within that community.


In late July, a 20-year-old man from New York’s Rockland County was found to have developed symptoms of polio, including paralysis. The man was unvaccinated, and no other cases have been identified thus far.


José Romero, director of the CDC’s National Center for Immunization and Respiratory Diseases, told CNN the one case detected last month could be “just the very, very tip of the iceberg.”


“There are a number of individuals in the community that have been infected with poliovirus. They are shedding the virus,” Romero said. “The spread is always a possibility because the spread is going to be silent.”


A vulnerable community: Rockland County is known to be a vaccine-resistant area, with the populace having a polio vaccination rate nearly 20 percentage points lower than the general U.S. population, according to the New York State Department of Health.


Last week, the New York State Health Department said the CDC had detected poliovirus through its wastewater surveillance. Six samples were collected from Rockland County across two months and five samples came from neighboring Orange County, which has a lower polio vaccination rate than Rockland.