In July, a man was diagnosed with polio in New York State’s Rockland County.

Officials say that polio has been in the county’s wastewater since May and New York City officials detected polio in the city’s wastewater earlier this month. Other countries that had not detected polio in decades have also confirmed new cases this year.

We speak with Apoorva Mandavilli from the New York Times about these cases of polio and what it would take to eradicate the virus completely.