Polio may be spreading in NYC, officials say after finding traces in the sewage. Here's what you need to know, from symptoms to risk of infection.

• New York City health officials identified the polio virus in wastewater.
• The wastewater findings suggest the virus is spreading locally in the city, health officials said.

New York City's Health Department has identified the polio virus in sewage in the city, the department announced on Friday.

The wastewater findings suggest the virus is spreading locally in the city, health officials said.

The statement adds that polio can lead to paralysis and death. The NYC Health Department urged those living in the city to get vaccinated against the virus now if they haven't already.

"With polio circulating in our communities there is simply nothing more essential than vaccinating our children to protect them from this virus, and if you're an unvaccinated or incompletely vaccinated adult, please choose now to get the vaccine," Dr. Ashwin Vasan, New York City's health commissioner, said in the statement.

"Polio is entirely preventable and its reappearance should be a call to action for all of us," he continued.

The findings come days after polio was first detected in a nearby New York county with high rates of vaccine refusal — the first case of polio in the US since 2013.

New York health officials estimated that "hundreds" of people in two counties neighboring New York City may have been infected with polio.

Health officials recently reported a small spread of the virus in London as well. The UK has been considered polio-free since 2003.

Polio, spread through food or water, was eliminated using a 4-dose vaccine

Polio, once one of the most serious transmissible diseases among children, had been eliminated in the US in 1979 because of widespread vaccination.

There had been no cases of polio caused by wild poliovirus originating in the US since 1979, but the virus had been brought into the country by travelers, the Centers for Disease Control and Prevention said.

Children typically get a four-dose polio vaccine that provides immunity for an unknown — but likely long — period of time. Federal law requires immigrants to get vaccinated against a slew of deadly viruses, and state law dictates rules about vaccination for schoolchildren.

Polio is transmitted through food or water contaminated with fecal matter from an infected person.

It can cause paralysis in one out of 200 infected people

Most people who contract polio do not have visible symptoms, and one out of four will experience flu-like symptoms, including sore throat, fever, and nausea.

A small proportion of people will experience more serious symptoms after contracting polio. The CDC said the virus could cause paralysis in one out of 200 infected people.

Children who seem to fully recovery from polio can develop muscle weakness, pain, or paralysis as an adult.

There is no cure for polio, but vaccines can prevent transmission. The rise of the anti-vaccine movement in the US in the past decade has stalled efforts to eliminate diseases, including COVID-19 and measles.