In the mid-20th century, the polio epidemic in the United States was so bad that it crippled tens of thousands of people each year. When the virologist Dr. Jonas Salk developed a successful vaccine in 1955, however, these numbers began to decline. Since 1979 there has not been a single case of wild poliovirus originating in the United States. (Some wild cases of poliovirus have been brought into the United States from other countries.) Even today, cases of polio of any kind are remarkably rare in this country.
However, a new tally of polio cases in upstate New York suggests polio outbreaks are not as rare as they used to be in the United States.
A federal team of scientists has been dispatched to New York by the Centers for Disease Control and Prevention (CDC) to study a number of polio cases in the state. It started in Rockland County, where a once-healthy young adult saw his legs become paralyzed after developing the first case of polio in nearly a decade. This patient is believed to have contracted polio through an oral vaccine, a type of which is no longer administered in the United States but is still used outside of the country. The oral vaccine uses a live, weakened version of the poliovirus.
News of a polio outbreak in the United States is unprecedented given the near-eradicated state of the disease. Polio vaccines are a standard supplement to vaccines distributed in the American health care system; Most children in the United States receive four polio shots between birth and age 6, as recommended by the Centers for Disease Control and Prevention (CDC). The CDC states that “almost all children (99 out of 100)” who are given these recommended vaccines are protected from the poliovirus.
Since the outbreak in upstate New York, experts have also been testing the sewage in New York’s Rockland County and its neighbor Orange County. To their dismay, the scientists found three sewage samples that tested positive for polio — as well as four others that were genetically linked to the previously confirmed case. Since the majority of people with polio do not develop symptoms, and many polio patients develop flu-like symptoms rather than paralysis, this suggests that there may be other infected individuals who simply do not know they are infected.
Given how rare polio is today, the polio outbreak in New York looks particularly grim. Indeed, the spate of anti-vaccination conspiracy theories that have been prominent over the past two decades has caused millions of Americans to avoid vaccinating their children or themselves due to misinformation. The specter of misinformation about vaccines looms over every outbreak of a nearly eradicated disease.
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But given the importance of polio vaccination, could an epidemic really spread beyond a small region like these two boroughs of New York? Notably, polio immunization rates in Rockland and Orange County are 60.34% and 58.68%, respectively. That puts them at the bottom: Of New York’s 62 counties, only one, Yates County, had a lower polio vaccination rate.
In other words, the polio outbreak could very well be related to anti-vaccination attitudes in rural Rockland County. Aside from the possibility that the Rockland County patient contracted polio because he took an oral vaccine, Rockland County actually has a large Hasidic Jewish community that sometimes votes against the vaccination. As The Times of Israel writes, there is a “violent backlash against vaccination” in certain Orthodox communities, “fueled by the COVID-19 pandemic and following a measles outbreak in Rockland County in 2018 and 2019 that affected Orthodox populations who concentrated Haredi in the region. “
“The risk of spreading polio is limited to those who have not received the polio vaccine,” Russell Medford, chair of the Center for Global Health Innovation, told Salon via email. “According to the CDC, nearly 93% of children in the United States are vaccinated by age [two].”
In 2018 and 2019, a group of Hasidic rabbis in that county experienced a measles outbreak related to anti-vaccination tendencies in their community that ruled out herd immunity; Measles is preventable through vaccination. Rockland County’s political leadership alluded to it last month.
“Our people have defeated measles and I am confident that we will also eliminate the latest health problem,” County Executive Ed Daly said at a July 21 news conference.
If you’re worried these polio outbreaks could lead to a larger pandemic, health experts assure you are almost certainly safe if you got your polio shot in the United States.
“The risk of spreading polio is limited to those who have not received the polio vaccine,” Russell Medford, chair of the Center for Global Health Innovation, told Salon via email. “According to the CDC, nearly 93% of children in the United States are vaccinated by age [two].”
dr Al Sommer, dean emeritus and professor of epidemiology at the Johns Hopkins Bloomberg School of Public Health, expressed a similar sentiment.
“It can certainly spread — infect someone without getting sick, but excreted by them and therefore ‘passed on,'” Sommer told Salon via email. “But it would be rare for someone who was vaccinated to be clinically affected even if they had encountered the virus.”
It’s also worth noting that the polio vaccine is considered permanent immunity, meaning it lasts a long time from the first vaccination. This is in contrast to COVID-19 vaccines, which are still overwhelmingly effective but require more frequent vaccinations to keep up with new strains. This type of immunity is called transient immunity; Influenza is an example of another virus where infection or vaccination confers only temporary or short-term immunity.
like dr Monica Gandhi, an infectious disease physician and professor of medicine at the University of California-San Francisco, Salon said there are two types of poliovirus vaccines, both of which work very well and provide durable immunity. “Both types of vaccines confer long-lasting immunity against disease development,” Gandhi said.
Still, Sommer says, there’s still reason for caution.
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“An outbreak can always occur when the virus is widespread in a largely unvaccinated community,” Sommer explained. “But since most Americans have historically been fully vaccinated, there’s little chance of it getting past the unvaccinated community or causing anything like COVID in the US.” Given the nature of the poliovirus (and its various variants) and the effectiveness of the polio vaccine (live and killed versions), we should not expect an epidemic or pandemic remotely like the COVID pandemic.”
“Based on past polio outbreaks, New Yorkers should know that for every observed case of paralytic polio, potentially hundreds of other people are infected.”
Should another major eruption occur, it could be devastating. During the mid-20th century polio outbreak in the United States, tens of thousands of people were paralyzed until Dr. Jonas Salk launched his polio vaccine in 1955. But even after that, these thousands of people lived with the consequences of the disease for the rest of their lives – while doing pioneering work for the disability rights movement.
This lasting memory perhaps explains why public health officials are also warning of the potential for a larger epidemic.
“Based on past polio outbreaks, New Yorkers should know that for every case of paralytic polio seen, hundreds of other people may be infected,” said State Health Commissioner Dr. Mary T. Bassett in a statement.
Bassett added: “In conjunction with the latest findings on wastewater, the Department is treating the individual case of polio as just the tip of the iceberg with a much larger potential spread. As we learn more, what we do know is clear: the threat of polio is present in New York today.”
The CDC has reassured the public that it is doing its best to stay informed about the potential pandemic.
“CDC continues to work with the New York State Department of Health to investigate their recent polio case, including ongoing testing of wastewater samples to monitor for poliovirus and sending a small team to New York to be on-site with investigation and immunization efforts to help,” a CDC spokesman told reporters Sunday.
It is noteworthy that the sample from the infected Rockland County patient bears genetic resemblance to samples found in sewage from Jerusalem and London, and Israeli and British cities respectively. This suggests that the poliovirus in question did not originate in the United States, although it is not certain.
The news also raises awareness of one of the most common criticisms of Albert Sabin’s vaccine, which, while usually effective, can on rare occasions produce a virus that mutates, regaining virulence and causing symptomatic polio infections. Most of the current polio cases worldwide have been caused by this vaccine, and specifically by a process that causes the virus to mutate into its more dangerous form as it passes through a patient’s intestines.
This type of poliovirus, known as type 2, cripples only 1 in 1,000 people who get it. Many others only show symptoms, such as diarrhea and a runny nose, and conclude that they are suffering from something more harmless.