During the middle of the 20th century, the polio epidemic was so severe in the United States that tens of thousands of people were paralyzed by it each year. Once the virologist Dr. Jonas Salk created a successful vaccine in 1955, however, those numbers began to plummet. Since 1979, there have been no cases of wild poliovirus originating in the United States. (Some cases of wild poliovirus have been brought into the United States from other countries.) Even today, cases of polio of any kind in this country are surprisingly rare.
However, a new crop of polio cases in New York state suggests that polio outbreaks are no longer as rare as they once were in the United States.
A federal team of scientists has been sent to New York by the Centers for Disease Control and Prevention (CDC) to investigate what appears to be a series of polio cases in the state. It started in Rockland County, where a previously healthy young adult watched his legs become paralyzed after developing the first case of polio seen here in nearly a decade. This patient is believed to have contracted polio from an oral vaccine, the type of which is no longer given in the United States but is still used outside 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 disease’s nearly eradicated status. Polio vaccines are a standard adjunct to the vaccines given in the US healthcare system; most US children receive four polio vaccines 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 receive these recommended vaccines will be protected from the polio virus.
Since the outbreak in New York state, experts have also tested wastewater in New York’s Rockland County and neighboring Orange County. To their dismay, the scientists found three sewage samples that tested positive for polio, as well as four others that were genetically related to the previously confirmed case. Since most people with polio develop no symptoms, and many polio patients only develop flu-like symptoms rather than paralysis, this suggests that there could be other infected individuals who simply do not know they are infected.
Given how uncommon polio is today, the polio outbreak in New York seems particularly foreboding. In fact, the flurry of anti-vaccination conspiracy theories that have been prominent in the past two decades has spurred millions of Americans to avoid vaccinating their children or themselves because of the misinformation. The specter of vaccine misinformation hangs over any outbreak of a nearly eradicated disease.
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However, given the importance of polio vaccination, could an epidemic really spread beyond a small region like these two New York counties? Notably, polio vaccination rates in Rockland and Orange County are 60.34% and 58.68%, respectively. That puts them at the bottom: Among New York’s 62 counties, only one, Yates, had the lowest polio vaccination rate.
In other words, the polio outbreak could very well be related to anti-vaccination attitudes in rural Rockland County. In fact, in addition to the possibility that the Rockland County patient contracted polio from taking an oral vaccine, Rockland County has a large Hasidic Jewish community that has at times harbored anti-vaccination sentiment. As The Times of Israel writes, there is a “fierce anti-vaccination backlash” in certain Orthodox communities, “fueled by the COVID-19 pandemic and following a measles outbreak in Rockland County in 2018 and 2019 that focused on the Haredi Orthodox population of the area.”
“The risk of spreading polio is limited to those who have not received the polio vaccine,” Russell Medford, president of the Center for Global Health Innovation, told Salon via email. “According to the CDC, in the US, almost 93% of children are vaccinated by age [two].”
In 2018 and 2019, a group of Hasidic rabbis in this county experienced a measles outbreak linked to anti-vaccine trends in their community that prevented herd immunity; measles can be prevented by vaccines. Rockland County’s political leadership alluded to this last month.
“Our people defeated measles, and I’m confident that we will also eliminate the last health problem,” County Executive Ed Daly said at a news conference on July 21.
If you’re worried that these polio outbreaks could lead to a larger pandemic, health experts say if you’ve gotten your polio vaccine in the U.S., you’re almost certainly safe.
“The risk of spreading polio is limited to those who have not received the polio vaccine,” Russell Medford, president of the Center for Global Health Innovation, told Salon via email. “According to the CDC, in the US, almost 93% of children 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 view.
“It can certainly be spread — infecting someone without causing illness, but being excreted by them and thus ‘transmitted,'” Sommer told Salon via email. “But it would be rare for anyone vaccinated to be clinically affected even if they encountered the virus.”
It is also worth noting that the polio vaccine is considered to confer long-lasting immunity, meaning that it lasts for a long time with just the initial inoculation. This puts them in contrast to the COVID-19 vaccines, which are still overwhelmingly effective but require more regular shots to keep up with the new strains. This type of immunity is called transient immunity; Influenza is an example of another virus for which infection or vaccination confers only transient or short-term immunity.
As Dr. Monica Gandhi, an infectious disease doctor and professor of medicine at the University of California-San Francisco, told Salon, there are two types of polio vaccines, both of which work very well and provide long-lasting immunity. “Both types of vaccines confer long-lasting immunity against disease development,” Gandhi said.
That said, as Sommer pointed out, there is still reason for some caution.
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“There can always be an outbreak if the virus is prevalent within a largely unvaccinated community,” Sommer explained. “But since most Americans have been fully vaccinated in the past, it has little chance of spreading beyond the unvaccinated community or causing anything like COVID in the US. Given the nature of the virus polio (and its various variants) and the effectiveness of the polio vaccine (live and dead versions), we should not expect any epidemic or pandemic remotely like the COVID pandemic.”
“Based on previous polio outbreaks, New Yorkers should know that for every case of paralytic polio observed, there may be hundreds of others infected.”
If another large outbreak were to 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. Even after that, however, those thousands of people lived with the ramifications of the disease for the rest of their lives, and helped pioneer the disability rights movement in the process.
That lingering memory may explain 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, there may be hundreds of other people infected,” State Health Commissioner Dr. Mary T. .Bassett.
Bassett added: “Along with the latest sewage findings, the Department is treating the single case of polio as just the tip of the iceberg of a much larger potential spread. As we learn more, what we know It’s clear: the danger of polio is present in New York today.”
The CDC assured the public that it is doing everything it can to stay on top of the potential pandemic.
“CDC continues to work with the New York State Department of Health to investigate its recent case of polio, including ongoing testing of wastewater samples for poliovirus and deploying a small team to New York to help on the ground with research and vaccination efforts,” a CDC spokesperson told reporters Sunday.
Notably, the sample from the infected patient in Rockland County shows genetic similarity to samples found in sewage in Jerusalem and London, 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 brings to light one of the common criticisms of Albert Sabin’s vaccine, which, while usually effective, can in rare cases produce a virus that mutates, regains its virulence, and causes polio infections symptomatic Most of the current cases of polio in the world were caused by this vaccine and, in particular, by a process that causes the virus to mutate into its most dangerous form as it passes through a patient’s intestine.
This type of poliovirus, known as type 2, paralyzes only 1 in 1,000 people who contract it. Many others will only show symptoms like diarrhea and runny nose and conclude that they are sick with something more innocuous.