Polio May Be Spreading, NYC Wastewater Data Suggests
Public health experts are worried that hundreds of people in the U.S. may be infected with the virus, which can lead to paralysis or even death.
At the end of last week, New York health authorities announced they had detected poliovirus in New York City sewage, raising concerns that the dangerous pathogen may be circulating more widely than first suspected. Poliovirus has also been found in wastewater samples collected in nearby Rockland and Orange counties.
Just one case of polio has been confirmed so far in an unvaccinated 20-year-old man from Rockland County who was hospitalized in June. This was the first polio case in the U.S. since 2013. The patient has reportedly experienced muscle weakness, temporary paralysis, and difficulties walking.
“For every one case of paralytic polio identified, hundreds more may be undetected,” said New York State Health Commissioner Mary T. Bassett, MD, MPH, in a statement. “The detection of poliovirus in wastewater samples in New York City is alarming, but not surprising.”
“To see even one polio case in the United States now is really a big step backwards,” says Yvonne Maldonado, MD, professor of global health and infectious diseases at Stanford University in California. “We need to really be aware of the importance of vaccinating our families and our kids to keep them from getting sick with diseases that are completely preventable.”
Why Polio Is So Dangerous
Polio is very contagious, and a person can spread the virus even if they aren’t showing signs of infection. Polio symptoms, which can be mild and flu-like (fatigue, fever, headache, stiffness, muscle pain, vomiting), can take up to 30 days to appear, during which time the individual can be shedding virus to others.
In rare instances, polio can cause total paralysis in a matter of hours, or even death.
The World Health Organization stresses that polio (also called poliomyelitis) mainly affects children under 5 years old, but people of any age can get it.
“The virus is spread in the intestinal tract in what we call the fecal-oral route,” meaning that it is shed in the stool of a host and enters the mouth of the next host through some means, says Dr. Maldonado. “There’s some evidence that it can be spread also in respiratory contact, but that’s much less common.”
Maldonado notes that the virus can travel through contaminated water, and in the 1940s through the '60s, many of those infected were thought to have caught the disease at pools, lakes, and other bodies of water. President Franklin Roosevelt contracted the illness at age 39 while vacationing in Canada, becoming paralyzed from the waist down.
Vaccination Stops Polio in Its Tracks
In the late 1940s, polio disabled an average of more than 35,000 people each year, according to the Centers for Disease Control and Prevention (CDC). After polio vaccines were introduced in the mid-1950s and early 1960s, the number of polio cases plummeted to less than 100 in the 1960s and fewer than 10 in the 1970s. The effectiveness of vaccination is undeniable.
Most adults in the United States were vaccinated against polio in their youth, says the CDC, but today a significant number of children are unprotected. In New York City, for example, only 86.2 percent of kids from 6 months to 5 years have received the recommended three doses of polio vaccine. (By age 6 children should have received a total of four doses). For 2-year olds, Rockland County has a polio vaccination rate of 60.34 percent and Orange County has a polio vaccination rate of 58.68 percent.
People who should get a polio vaccine include those who are unvaccinated, including pregnant individuals; those who have not completed their polio vaccine series; and those who are concerned they might have been exposed by someone in their community.
If you have any doubt about your vaccination status, ask your doctor to review your immunization record. If no record is available, it can’t hurt to be on the safe side and get vaccinated again, according to Maldonado.
Adults who are already vaccinated but are at risk of exposure are advised to receive a booster.
“Based on what we know about this case [in Rockland County], and polio in general, the Department of Health strongly recommends that unvaccinated individuals get vaccinated or boosted with the FDA-approved inactivated poliovirus vaccine as soon as possible,” said Dr. Bassett in a statement. “The polio vaccine is safe and effective, protecting against this potentially debilitating disease, and it has been part of the backbone of required, routine childhood immunizations recommended by health officials and public health agencies nationwide.”
'This Is Not a Disease You Want to Fool Around With'
William Schaffner, MD, an infectious disease specialist and professor of preventive medicine and health policy at the Vanderbilt University School of Medicine in Nashville, Tennessee, says the United States has been lucky so far not to see another confirmed case.
“No matter where you are — in Dubuque or in California or in Tennessee — this is not a disease you want to fool around with,” said Dr. Schaffner. “If you or your children are unvaccinated, run — do not walk — and get vaccinated against polio.”
Schaffner warned that even people who are vaccinated may still acquire the virus, have it in their intestinal tract, and transmit it.
“It probably won’t bother you if you’re vaccinated, but you can spread it to other people,” he says. “And it won’t bother them as long as everybody’s vaccinated.”
Poliovirus Can Originate From Oral Vaccines
Health experts determined that the single polio case detected in the United States so far was “vaccine-derived.” That means the infection likely originated in someone who’d received an oral polio vaccine (OPV), which uses live, weakened poliovirus, and is given in the form of drops in the mouth.
This type of vaccine hasn’t been used in the United States since 2000, when the country moved exclusively to using inactivated poliovirus vaccine (IPV).
Oral polio vaccines continue to be used elsewhere in the world, and they are extremely effective. The risk of getting paralysis from vaccine-derived polio is far lower than the risk from the original, naturally occurring “wild-type” form of the virus. Research suggests about 1 in 1 million oral polio vaccinations lead to paralytic disease. Maldonado, who has extensively researched polio, estimates that about 1 in 100 wild-type infections results in paralysis.
Polio Is Also Spreading Outside the U.S.
A month before this U.S. case was detected, health authorities in the United Kingdom issued an alert that they had found poliovirus in wastewater in London, suggesting it was spreading there. On August 10, after sewage analysis revealed further poliovirus, the U.K. government recommended that healthcare providers offer polio vaccine booster to children across London.
For the week ending August 12, the Global Polio Eradication Initiative reported more polio cases in the Democratic Republic of the Congo, Mozambique, and Yemen.
In response to the polio detection in the United States, the Global Polio Eradication Initiative called upon all countries — in particular those with a high volume of travel and contact with polio-affected countries and areas — to strengthen surveillance in order to rapidly detect any new virus and facilitate a rapid response.