More Polio Virus Found in New York Wastewater

That confirmed case was in an unvaccinated adult resident of Rockland County who developed symptoms including weakness and paralysis starting in June.

“New Yorkers should know that for every one case of paralytic polio observed, there may be hundreds of other people infected,” State Health Commissioner Mary T. Bassett said in a statement on Thursday. “Coupled with the latest wastewater findings, the Department is treating the single case of polio as just the tip of the iceberg of much greater potential spread.”

The new findings don’t imply that the identified case in Rockland County is the source of the transmission, according to the New York State Department of Health. An investigation into the origins of the case is continuing.

New York health officials urged those who are unvaccinated or not fully vaccinated against polio to get immunized immediately. Unvaccinated people who live, work, go to school in or visit Rockland County, Orange County or the greater New York metropolitan area are at the greatest risk of exposure.

Officials have said that people who are fully vaccinated are at very low risk of contracting the disease.

The poliovirus is highly transmissible and is spread mostly when a person touches their mouth after coming into contact with an infected person’s feces. It can spread asymptomatically, a concern among health officials. Just over 70% of people have no symptoms at all, according to the CDC, and about a quarter develop flulike symptoms.

The virus can also affect the brain and the spinal cord, and about one in 200 people with a poliovirus infection will have weakness in the arms and legs or paralysis, which is often permanent. Up to 10% of paralyzed patients die when the muscles that help them breathe are immobilized.

Good hand hygiene is also critical for preventing infection, said Vincent Racaniello, a microbiology and immunology professor at Columbia University who studies poliovirus. “They can have contamination on their hands, shake hands with someone else, and that starts an infection.”

Two forms of the virus currently cause outbreaks, one being the wild poliovirus found in nature. Cases also can be caused by vaccine-derived poliovirus, which occurs when a weakened strain in an oral polio vaccine used in some parts of the world mutates and then infects someone else when they come into contact with feces of the recently vaccinated person. The U.S. no longer administers that vaccine but instead uses an inactivated vaccine that doesn’t contain live virus.

The case in Rockland was caused by a vaccine-derived strain of the virus, officials said.

The U.S. no longer administers that vaccine but instead uses an inactivated vaccine that doesn’t contain live virus and protects some 99% of children who are fully vaccinated, health officials said.

Other countries have used wastewater surveillance to search for the poliovirus before the practice was more widely adopted to track the virus that causes Covid-19. But sewage monitoring for polio isn’t common in the U.S., where no cases of the infection have originated since 1979.

The positive sewage samples from New York in June were tested for poliovirus retrospectively, after being collected as a part of the Covid-19 wastewater monitoring program, a state health department spokesperson said. The department then started screening new July samples for poliovirus and plans to continue ongoing surveillance efforts with the CDC.

In June, U.K. health officials also detected polio in London’s wastewater system, putting the country on high alert. The Global Polio Laboratory Network, established in 1990 by the World Health Organization and national governments, confirmed in late July that the samples from London’s wastewater are genetically connected to both the case in New York and recent wastewater samples from Israel, according to the Global Polio Eradication Initiative.

Global health experts have said that polio eradication is within reach, after a decadeslong worldwide vaccination campaign. The wild-type virus is now endemic in only two countries, Afghanistan and Pakistan, and they are close to eliminating it. Yet international crises including the Covid-19 pandemic have recently dealt setbacks to the effort.

Most of the U.S. population is vaccinated against polio, and the inoculations are a part of the CDC’s standard child immunization schedule and required in New York for all school-age children, unless they have a medical exemption.

Rockland County and Orange County, however, both have below-average vaccination coverage. Among 2-year-olds in the state, the polio vaccination rates for three doses are about 60% and 59% in Rockland County and Orange County, respectively, compared with a statewide average of about 79% vaccinated, according to the New York State Department of Health.

Dr. Racaniello said that the U.S. vaccination rates against polio are high enough that he isn’t concerned about bigger outbreaks. “The problem is you have communities where many kids are not vaccinated,” he said. “There, if the virus gets in, it’s going to spread and cause paralysis.”

Rockland County was also an epicenter of the 2019 measles outbreaks in the state, with cases in that outbreak largely occurring among close-knit Orthodox Jewish communities there.

The Rockland County Department of Health has set up polio vaccination clinics following the confirmed case. Officials also said in July that they sent some 3,000 letters to families whose children weren’t up-to-date with vaccinations and plan to review immunization information at the start of the school year.

Write to Brianna Abbott at brianna.abbott@wsj.com

Corrections & Amplifications
The last polio case that originated within the U.S. occurred in 1979. An earlier version of this article incorrectly said that the virus was eliminated from the U.S. in 1978. (Corrected on Aug. 5)