The disease was mostly eradicated after a vaccine was developed. The New York City health authorities said on Friday that they had found the virus in wastewater samples and that it was likely that there was a resurgence of the disease.

For the first time in generations, parents of young children were questioning how much they should worry about the disease.

A designer who lives in Brooklyn's Crown Heights neighborhood said she had friends whose children probably weren't vaccine proof. She said she would make her friends aware.

Ms. Borges hopes that her 7-month-old daughter, who has had three of the four shots recommended for children, will be protected. Ms. Borges said thatPolio is dangerous for babies like her.

In New York City, the vaccine rate for children under the age of 5 is 86 percent, and most adults in the United States received a vaccine against the disease as children. In some city ZIP codes, less than two-thirds of children under the age of five have received at least three doses of the vaccine.

The state Health Department said in a statement that the discovery of the virus underscored the need for every New York adult and child to get immunizations.

Three weeks ago, a man in Rockland County, N.Y., north of the city, was diagnosed with a case of the disease that left him with paralysis. According to officials, there has been a circulating of the disease in the wastewater.

The risk to New Yorkers is real but the defense is simple. If you are an unvaccinated or in completely vaccine-free adult, please choose to get the vaccine now because there is nothing more important than protecting our children from the ravages of the disease.

The current vaccine provides at least 99 percent protection against severe disease if given three times. Children who are too young to be fully immunised are vulnerable, as are children whose parents have refused to have them get the shots.

There are concerns that the detection of the disease in New York City's wastewater could lead to other cases.

The former deputy city health commissioner said it was likely they would be one or more cases in the city.

As the spread of misinformation about vaccines increased, the city's vaccine rate fell. Health officials were concerned about low vaccine rates in some neighborhoods before Covid came along.

The vaccine used in the US in recent decades is not as effective as it could be. Even if they don't have symptoms, people who have been vaccined can still carry and excrete the virus.

The state Health Department spokeswoman said that it may mean the virus will be hard to eradicate quickly.

Many people don't develop symptoms after being bitten by the disease, but some people do. Dr. Bernard Camins, an infectious diseases specialist and medical director of infection prevention for the Mount Sinai Health System, urged doctors to be on the lookout for those symptoms and to consider ordering a vaccine for patients who are not fully protected.

According to the health authorities, about 4% of those who contract the virus get viral meningitis, and 1 in 200 will be paralyzed.

If you have one case of paralysis, there may be hundreds of others that aren'tsymptomatic or have symptoms that aren't likely to be associated with the disease.

It was the first sign of the disease in New York City after it was found in wastewater in Rockland and Orange Counties.

The city and state health departments didn't give any information about where the virus had been found. Six positive samples of concern have been identified in the city's wastewater.

The United States has not had a case of the disease in over a year.

Prior to the introduction of the vaccine, the virus was a source of fear, especially during the summer. Parents kept their children indoors when swimming pools were closed as a preventative measure.

In 1916, 6,000 people in the United States were killed by the disease and another 21,000 were left with a permanently disabled child. The outbreak caused a delay in the opening of public schools in New York City.

Many children were left with iron lungs due to an outbreak in 1952. After the vaccine came out, the virus began to diminish.

Pakistan and Afghanistan are the only places in the world where the disease is endemic. Vaccines have kept it out of the rest of the world.

The oral vaccine that is used in much of the world has led to cases appearing outside of those two countries. The oral vaccine is live. A person who gets it can spread the weakened virus to other people. In the United States, the only vaccine that has been used is inactivated.

The Centers for Disease Control and Prevention is seeing a wake-up call for people who thought that there was no need to worry about the disease.

Most of the time, the virus is spread through contact with feces.

According to the C.D.C., if the weakened virus used in the oral vaccine circulates widely enough in communities with low vaccination rates or if it replicates in a person with a compromised immune system, it can cause paralysis.

In the last few years, there have been many cases of vaccine-derived polio in countries. The spread can be aided by open sewer and contaminated water.

The health authorities believe that the disease was introduced to New York by an unvaccinated person who got the vaccine while abroad.

The virus detected in the two counties north of New York City is genetically linked to vaccine-derived virus collected from samples this year in Jerusalem, as well as to wastewater samples in London that have led to a renewed vaccine campaign there, according to officials.

The C.D.C. confirmed the presence of the disease in 20 wastewater samples in Rockland and Orange counties. Each county is next to another.

Two samples were collected in May and three in June and eight in July from Rockland County.

Dr. Gelman said she was waiting for further genetic analysis from the C.D.C. to be sure, but she said officials were assuming that each positive sample indicated a separate person.

Hundreds of people in the area could be affected by the disease. The estimate is based on how many people would need to get the vaccine in order for there to be a single case of the disease.

She hopes that doesn't happen.

A perfect storm scenario is being worked on. There are low vaccination rates for vaccine preventable diseases among our children.

According to several local officials, a 20-year-old male ultra-Orthodox Jewish resident of Rockland County is the only person to have been diagnosed with the disease. Anti-vaccine sentiment has spread among some in the ultra-Orthodox Jewish community in Orange and Rockland counties.

There was an outbreak of the disease in the ultra-Orthodox community, but vaccine misinformation and low vaccine rates were also found more widely.

The state Health Department says that the vaccine rates in Rockland and Orange Counties are not high enough. State data shows that 60 percent of children in both counties had all three immunizations.

New Yorkers were alarmed by the recent emergence of monkeypox and wondered if they had been fully protected.

Gregory is a Crown Heights resident who works as a Porter. He said that they are up to date on their vaccinations, but three of them are younger than 5.

He said he was scared of it because he and his friends hadn't heard about the disease. All you can do is put your faith in God and hope that doesn't happen with your child

She contributed to the report.