A case of polio has been identified in an unvaccinated adult man in Rockland County, officials said.

The New York State Department of Health and its Rockland County counterpart confirmed that the infection was transmitted from someone who received the oral polio vaccine, which has not been administered in the United States since 2000. Officials said in a news release that the virus may have originated outside the United States, where the oral vaccine is still administered.

“I want to stress that this individual is no longer contagious,” said Ed Day, the Rockland County executive, in a news conference Thursday afternoon. “Our efforts now are focused on two issues: vaccinations and figuring out if anyone else has been impacted by this disease.”

Those who are unvaccinated or haven’t completed their vaccination series should get vaccinated, officials said. The current polio case presents a very low risk to those who are already vaccinated against polio: Those who have had all three shots have close to 100 percent protection.

The person’s symptoms began about a month ago, said Dr. Patricia Schnabel Ruppert, Rockland County’s health commissioner, at the news conference. The patient presented with “weakness and paralysis,” she said, and the department was notified on Monday about the confirmed case.

“We are now surveying the family and close contacts of this individual to assess the risk to the community,” Dr. Ruppert said. She did not share any additional information about the patient’s current state of health or prognosis.

Although the health officials did not reveal the gender of the patient, local elected officials said he is a man from the Orthodox Jewish community. In 2018 and 2019, there was a measles outbreak in Rockland County concentrated among ultra-Orthodox Jewish people, whose vaccination rates have tended to be lower than the broader population. In that outbreak, more than 150 people were infected with the measles.

The last case of polio in the United States was in 2013, in someone who brought the disease in from abroad. There has not been a case originating in the United States since 1979, according to the Centers for Disease Control and Prevention.

The disease was one of the most feared in the country until the 1950s, when the first vaccine was developed.

Sixty percent of Rockland County’s 2-year-olds have received all three doses of the polio vaccine, according to state data — a considerably lower rate than the 80 percent rate in the rest of the state excluding New York City.

To achieve herd immunity for polio, the target vaccination rate is 80 percent, according to the World Health Organization.

Disruptions caused by the Covid-19 pandemic depressed vaccination rates for routine immunizations for children around the globe and in the United States, according to some studies. Misinformation and mistrust related to Covid vaccines have also affected childhood vaccination rates, as more parents have expressed fears about long-established vaccines.

Dr. Amesh A. Adalja, senior scholar at Johns Hopkins Center for Health Security, said that vaccine hesitancy could give vaccine-derived polio strains “an opportunity to cause damage” in a community that has large pockets of unvaccinated people.

Polio is very contagious, the Health Department said in a news release. People can spread the disease even if they do not have symptoms, which can include fatigue, fever, headache, muscle pain and vomiting. Rarely, polio cases may result in paralysis or death.

The oral vaccine is safe and effective and is still given in countries where vaccine access is more limited. However, people who receive the oral vaccine, which contains a weakened version of the virus, may shed the virus.

The shedding feature was initially thought of as an advantage, Dr. Adalja said.

“It mimics natural infection, and people shed the virus, the vaccine virus, and that spreads to other people, and then they get immunized that way,” he said. In very rare cases, the virus in the vaccine can mutate as it travels from person to person and lead to paralysis in someone who is not vaccinated, he said.

The United States uses an injected polio vaccine that contains inactivated virus instead of live virus.

Jesse McKinley contributed reporting.