Polio Rears Its Ugly Head in America
“Until polio is wiped out worldwide, all countries are at risk of a resurgence. Polio can be a plane ride away, if it is out there somewhere.”
- Dr. Ananda Bandyopadhyay, Deputy Director of Polio Technology, Research & Analytics, Bill and Melinda Gates Foundation
“Coupled with the latest wastewater findings, the department is treating the single case of polio as just the tip of the iceberg of much greater potential spread.”
- Mary Bassett, M.D., MPH, New York State Health Commissioner
Due to the administration of highly effective and safe vaccines, poliomyelitis (polio) was eliminated from the U.S. in 1979 and from the U.K. in 2003. But on June 22, 2022, U.K. health officials found evidence of poliovirus (PV) in samples from London’s sewage. Then on July 21, 2022, New York state health officials reported a case of paralytic polio in an unvaccinated young adult resident of Rockland County (a suburb of New York City). Both of these findings set off an alarm. How could this happen when polio had been eliminated from both the U.K. and the U.S. and the worldwide eradication of polio seemed imminent? (For prior Germ Gems posts on polio, see “Eradication of Polio: Stuck in the Red Zone,” October 11, 2019 and “Stumbling Blocks in the Road to Polio Eradication,” April 27, 2022.)
To put it bluntly, we let our vaccination guard down. Polio is a highly contagious disease but can be prevented. If you and your family members are fully vaccinated, you have nothing to worry about. In this Germ Gems post, I summarize what everyone needs to know about the scourge of polio and put the recent developments in New York and London in perspective.
The road to polio eradication. PV is an enterovirus, meaning it infects cells lining the gastrointestinal tract. Polio is spread primarily through contact with the feces of an infected person (fecal contamination of hands, utensils, food and water) but can also be transmitted via droplets from coughing.
About three quarters of people who are infected by PV are asymptomatic yet contagious. Those who do get sick can develop fever, fatigue, headaches, muscle pain, and nausea. Only rarely (in less than 1% of infected people), does PV invade the bloodstream and enter the nervous system resulting in paralysis and, in some cases, death.
In the late 1940s, polio disabled an average of 35,000 Americans each year and was striking panic throughout much of the world. The introduction of two polio vaccines: Salk’s inactivated PV vaccine (IPV) in 1955 and Sabin’s oral PV vaccine (OPV) in 1961 and their attendant vaccination programs led to a precipitous decline in polio cases worldwide, falling from an estimated 350,000 cases globally in 1988 to just 33 cases in 2018—a 99.99% reduction.
These vaccines are aimed at three different strains of “wild polio virus” (WPV): WPV1, WPV2, and WPV3. In 2015, WPV2 was eradicated (that is to say, it’s gone from the face of the Earth), and in 2019 WPV3 was eradicated, leaving WPV1 which is endemic only in Pakistan and Afghanistan.
Unfortunately, in the early years of the 21st century, one of the attenuated (weakened) strains in the OPV “went rogue,” that is, it regained its virulence allowing it to cause paralysis. While people who were vaccinated with this OPV strain were protected, they could briefly shed the virus (via feces) and, in a community with a low vaccination rate, spread the virus.
The risk of developing polio from this OPV strain while rare was real and caused the U.S. to discontinue use of the OPV vaccine in 2000. Nonetheless, many other countries in the world continue to use OPV due the ease of administrating this vaccine.
Circulating vaccine-derived polio virus type 2 (cVDPV2) is the strain in the OPV that has caused major havoc in many areas of the world. If you are unvaccinated, you are at risk of developing polio if you are exposed to cVDPV2. Also, if you’re unvaccinated and travel to certain countries where WPV1 is a problem, you’re at risk if you become exposed to it.
In 2020, cVDPV2 caused 959 cases of polio worldwide. It is also the culprit in the recent case of polio in New York and is the strain found in sewage samples in London. (In early August, officials announced that cVDPV2 was detected in wastewater from Rockland and Orange Counties and most recently in wastewater of New York City.)
How did cVDPV2 find its way to Rockland County and London? Shortly after the unvaccinated adult in Rockland County with cVDPV2 polio was identified, it became clear that this was a case of exposure to the mutated form of the virus in the OPV obtained from outside the U.S. As it turned out, public health officials were quite familiar with Rockland County because in 2019 this was the site of an explosive measles outbreak in a tight-knit Orthodox Jewish community with anti-vaccination members. But exactly where this cVDPV2 strain originated remains a mystery.
Based on earlier polio outbreaks, New York Health Commissioner Dr. Mary Bassett expressed concern stating, “[F]or every one case of paralytic polio observed there may be hundreds of other people infected.” Given the recent finding of the virus in the wastewater including New York City and fearing silent spread of cVDPV2 throughout the community, New York health officials are considering offering children in the area an extra shot of IPV.
Similar to the situation in New York, the origin of the cVDPV2 isolate in London’s sewage is a mystery. Public health officials in the U.K. did find low vaccination rates in areas where the virus was isolated and appear to be facing the same challenges as those in New York.
Preventing polio: Vaccination is key. Polio vaccine is enormously effective at preventing polio. The breakthrough infection in New York and the recent potential for polio in London represent failures not of the vaccine but rather the failure to get everyone vaccinated.
In 1988, the World Health Assembly passed a resolution to eradicate polio. Together with its partners (Rotary International, the Centers for Disease Control and Prevention, and UNICEF), the World Health Organization launched the Global Polio Eradication Initiative (GPEI). Credit for the dramatic reduction in polio cases (by 99.99%) since then goes largely to the GPEI. According to an article in Lancet on May 28, 2022, “Pushing for polio eradication,” the GPEI’s new Polio Eradication Strategy 2022-2026 aims to eradicate polio by 2026. It recognizes the necessity to stop cVDPV2, and scientists have developed a new oral vaccine, novel oral polio vaccine type 2, designed for this purpose. According to the GPEI, more than 300 million doses of nOPV2 have been administered in 15 countries since March 2021.
Vaccination is key to ridding the world of polio. If the GPEI global polio vaccination campaign is successful in eradicating polio by 2026, we can then add PV to smallpox in the dustbin of eradicated human pathogens. And, most important, we will have protected our children not only today but also all future generations from this preventable disease.