The positive wastewater samples were found in Rockland County, where health authorities revealed two weeks ago that a man in his 2os had been paralyzed by so-called vaccine-derived polioviruses, and in neighboring Orange County as well. Positive samples were collected in June and July in Orange County and in July in Rockland County, suggesting that viruses have been spreading for some time.

Rockland and Orange counties have among the lowest vaccination rates for polio in New York State. Only 60% of young children in Rockland County have had the three doses of polio vaccine they should have received by their second birthday; in Orange County, the rate is 59%. While positive wastewater samples haven’t been reported from nearby Sullivan County, it too has a dismal polio vaccination rate for 2-year olds, 62%.

Those low vaccination rates suggest young children in all three counties are at risk of contracting polio if they remain unvaccinated.