The polio virus has been found in wastewater at a New York City suburb dating back to June.
The finding showed the virus had possibly been present in the community before the first confirmed case of the disease in almost a decade was diagnosed last month.
The water sample was taken from Rockland County as part of surveillance efforts for Covid-19, and was tested for polio last week after concerns sparked by the new case, which revealed the presence of a poliovirus strain, health officials said on Monday.
Laboratory tests also confirmed the strain in the case is genetically linked to one found in Israel, although that did not mean the patient had travelled to the country, officials added.
Genetic sequencing also tied it to samples of the highly contagious and life-threatening virus in the UK, said the US Centers for Disease Control and Prevention (CDC).
The presence of the virus in wastewater was an indication that more people in the community could be shedding the virus in their stool, the CDC said in an emailed statement.
The health agency, however, added there were no new cases identified and explained that it was not clear yet if the virus was actively spreading in New York or elsewhere in the US.
An adult was confirmed to be suffering from polio on 21 July, in the first case of the disease in the US in almost a decade.
The patient had started exhibiting symptoms in June, when local officials asked doctors to be on the lookout for cases, according to the New York Times.
“Further investigations – both genetic and epidemiological – are ongoing to determine possible spread of the virus and potential risk associated with these various isolates detected from different locations around the world,” the Global Polio Eradication Initiative said in a statement.
“Given how quickly polio can spread, now is the time for every adult, parent, and guardian to get themselves and their children vaccinated as soon as possible,” state health commissioner Dr Mary Bassett said.
The New York State Department of Health told Reuters that based on available evidence, it was not able to conclude for certain whether positive polio samples stemmed from the case identified in Rockland County.
“Certainly, when samples such as these are identified, it raises concerns about the potential of community spread - which is why it is critically important that anyone who is unvaccinated, particularly in the Rockland county area, gets vaccinated as soon as possible,” the department said.
Polio – a highly contagious and potentially deadly virus that has paralysed or killed millions of children around the world before aggressive vaccination attempts began – still has no cure.
It can only be prevented by vaccination.
New York officials have said they are opening vaccine clinics to help unvaccinated residents get their shots.
Inactivated polio vaccine (IPV) is the only polio vaccine that has been given in the US since 2000, according to the CDC. It is given by a shot in the leg or arm, depending on the patient’s age.
Polio is often asymptomatic and people can transmit the virus even when they do not appear sick. But it can produce mild, flu-like symptoms that can take as long as 30 days to appear, officials said.
It can strike at any age but the majority of those affected are children aged three and younger.
While many countries like the US had not seen a polio case in years, the disease has not been entirely extinct. Cases have, however, dropped significantly over the last couple of decades.
Additional reporting by agencies
