Polio may have been circulating in New York as early as April, and the virus has been detected in sewage samples more than 20 times, according to a report from the Centers for Disease Control and Prevention (CDC).
The agency released its first investigative report on a potential polio outbreak on Tuesday. The investigation comes in response to a confirmed case of polio in an unvaccinated man in his 20s in Rockland County, just outside New York, in June. Officials fear there could be hundreds — if not thousands — of undiagnosed cases in the state.
Only about one in every 1,900 polio infections in unvaccinated people will result in paralysis, according to the CDC.
While cases transmitted in the US are rare, the infected man had not recently traveled outside the country and had attended a large gathering eight days before his symptoms began. It is likely that he caught the virus in the state. The man suffered paralysis and was hospitalized.
He is now recovering at home, but it is not known if he is still paralyzed.
The CDC says the virus was detected in sewage samples in Rockland and nearby Orange County 20 times in samples collected in May, June and July. A single sample from Orange County in April also had an incomplete polio sequence, potentially indicating that the virus was already present four months earlier.
Both Rockland and Orange County have low vaccination rates — only 60 percent of people are vaccinated by their second birthday, well below the 95 percent threshold set by the World Health Organization (WHO). The CDC sent a team to Rockland last week to investigate and help introduce the vaccine to those in the community who have not yet received it.
Officials assure the public that a vaccinated person need not worry about the current epidemic. More than 90 percent of Americans are vaccinated by their second birthday — and many had to get the shot in order to attend public school. There is no booster vaccine against polio, and vaccination in childhood provides protection throughout a person’s life.
The CDC says the Rockland County man who was confirmed to have a polio infection had not traveled outside the U.S. during the seven to 21 days when symptoms typically appear. He attended a local meeting eight days before the onset of symptoms
Polio has been detected in sewage from New York City, Rockland County, and Orange County, New York. Although only one case was confirmed, sampling detected the virus more than 20 times
“The occurrence of this case, combined with the identification of poliovirus in sewage in neighboring Orange County, underscores the importance of maintaining high vaccination coverage for the prevention of polio in persons of all ages,” the CDC wrote in its report.
The infected man initially had a fever, stiff neck, stomach problems and weakness in the limbs.
He was hospitalized and a stool sample later confirmed that he had a case of polio from the vaccine.
This form of the virus comes as a result of the oral poliovirus vaccine (OPV). The vaccine delivers a live version of the virus to humans. While the body will usually kill the virus – making antibodies – in some rare cases the recipient will become infected.
OPV is no longer used in the US, instead being replaced by the inactivated polio vaccine (IPV), which is delivered by injection.
Some developing countries still use OPV because it is more readily available and activates antibodies faster than IPV.
Officials have not yet determined how the man was exposed to vaccine-induced polio.
Paralytic polio often takes seven to 21 days for an infected person to experience symptoms. The man did not travel outside the country during that period, yet he attended a large gathering of some sort eight days before the onset of symptoms that officials speculate may have been exposure.
Common symptoms of polio include high temperatures, extreme fatigue, headaches, vomiting, stiff neck and muscle aches
“Based on previous polio outbreaks, New Yorkers should know that for every observed case of paralytic polio, there may be hundreds of other people infected,” Dr. Mary Bassett, the state’s health commissioner, said last week.
A local Rockland official cautioned that the true number of cases in the Empire State is likely in the thousands.
“It’s not just one case of polio when you see a paralytic case. The incidence of paralytic polio is less than one percent,” Rockland County Health Commissioner Dr. Patricia Schnabel Ruppert told the BBC.
“Most cases are asymptomatic or mildly symptomatic and we often miss these symptoms.
“So there are hundreds, maybe thousands of cases that have happened for us to see a paralytic case.”
After the discovery of this first case, the CDC began surveillance of the virus in Rockland County and other local communities.
Local officials have already been taking sewage samples as part of their COVID-19 surveillance, which has allowed the agency to trace back and find older traces of the virus.
The CDC says that for every 1,900 cases of polio in an unvaccinated person, only one will develop symptoms of paralysis (polio virus illustration)
A total of 260 samples from Rockland and Orange counties were tested. Of that group, 13 samples from Rockland and eight from Orange were found to contain traces of the virus.
One Orange County sample from April still had an incomplete sequence of the virus. That said, it may or may not be related to the Rockland County case.
In the time since the report was closed on August 10, New York City officials have also confirmed the discovery of polio while monitoring wastewater.
“The risk to New Yorkers is real, but the defense is so simple – get vaccinated against polio,” said Dr. Ashwin Vasan, Municipal Health Commissioner.
“With polio circulating in our communities, there is simply nothing more important than vaccinating our children to protect them from this virus, and if you are an unvaccinated or incompletely vaccinated adult, please choose to get the vaccine now.
“Polio is completely preventable and its reappearance should be a call to action for all of us.”
New York City has an 86 percent vaccination rate. While better than Rockland and Orange counties, it still falls short of the 95 percent threshold set by the WHO.