Polio — once one of the most feared diseases in the United States, with annual outbreaks causing thousands of cases of paralysis — was considered to be eliminated in 1979 after widespread vaccination halted routine U.S. spread. But the virus has been brought into the country by travelers.
Evidence of expanding community spread has landed the United States on a list of more than 30 countries with active circulation of a type of polio known as vaccine-derived polio virus. It also prompted New York Gov. Kathy Hochul to declare a state of emergency Friday, authorizing paramedics, midwives and pharmacists to administer polio vaccinations, among other steps, to accelerate immunization rates. The emergency order also directs health-care providers to update the state with data on immunizations.
Some Biden officials expressed concern that there hadn’t been more active preparation for a possible polio outbreak, and called on the federal government to expand the testing of sewage across the nation and bolster vaccination campaigns. White House leaders have largely focused on gathering data to determine the outbreak’s potential spread.
There are two types of polio vaccines. The United States and many other countries use shots made with an inactivated version of the virus. But some countries where polio has been more of a recent threat use a weakened live virus that is given to children as drops in the mouth. Even though the oral vaccine is easier to administer and may give longer-lasting immunity, it has a key disadvantage: It can lead to vaccine-derived polio, a strain of which was identified in the unvaccinated Rockland County patient. Oral polio vaccine has not been used or licensed in the U.S. since 2000 because of that risk.
In rare instances, the weakened virus from the oral vaccine can mutate into a form capable of sparking new outbreaks. Transmission is most likely to occur in communities with low rates of vaccination against polio, allowing prolonged spread of the weakened live polio virus. As the virus circulates and more genetic changes occur, the virus can revert to a form that infects the central nervous system and causes illness and paralysis if it circulates in under-immunized populations or replicates in an immunocompromised person, according to the CDC.
Health officials say this kind of polio is not caused by a child receiving the polio vaccine. Polio vaccination protects people against naturally occurring polio viruses as well as vaccine-induced polio viruses. The U.S. population is highly vaccinated, with 93 percent of 2-year-olds having received at least three doses of polio vaccine, according to CDC data.
But unvaccinated people are at high risk in areas with low vaccination coverage, such as the ultra-Orthodox Jewish community in Rockland County where only about 60 percent of children have had three doses of the polio vaccine by their second birthday.
Federal officials recommend four doses of the polio vaccine: to be given when children are 2 months old, 4 months old, 6 to 18 months old, and between 4 and 6 years old. Some states require only three doses.
“On polio, we simply cannot roll the dice,” New York State Health Commissioner Mary Bassett said in a statement last week. “If you or your child are unvaccinated or not up to date with vaccinations, the risk of paralytic disease is real.”
No additional cases of polio have been reported in the United States. But sequencing of the virus detected in the wastewater samples by New York State shows those samples to be genetically linked to the virus sequenced from the stool sample of the Rockland County man, CDC officials have said.
In selecting the sites for additional wastewater testing, the CDC is weighing the community’s vaccination coverage, the extent of travel to and from countries where polio is still circulating, and whether the agency is already conducting wastewater surveillance for the coronavirus.
Wastewater surveillance has been used for decades around the world to contain polio outbreaks because people with the virus shed it in their stool. But testing for the polio virus has not been a formal part of the nation’s wastewater surveillance system launched by the CDC in September 2020 to monitor the spread of the coronavirus. That system, currently monitoring for SARS-CoV-2 in 46 states, five cities and two territories, is expanding to monitor for monkeypox in multiple communities over the next four to six weeks, CDC officials said.
The CDC has a plan to conduct more widespread wastewater testing for polio, but the agency cautions that expanding the system to test for new diseases takes time and resources to make sure there is “reliable, actionable data,” CDC spokesperson Kristen Nordlund said in a statement.
As part of a public campaign to encourage vaccination, Bassett and CDC Director Rochelle Walensky sent letters in English, Spanish, Haitian-Creole, and Yiddish last month to residents in Rockland, Orange, and Sullivan counties, warning that paralysis from polio is typically permanent and that 5 to 10 percent of those paralyzed die when their breathing muscles become immobilized. Similar letters will be sent soon to those living in Nassau County, according to New York State Health Department spokeswoman Samantha Fuld.
The polio virus lives in the throat and intestines and is very easily spread through contact with feces or, less commonly, through droplets from a cough or sneeze. There is no treatment for polio.
Most people who contract polio don’t have any visible symptoms, according to the CDC. About 25 percent develop flu-like symptoms, including headache, fever and nausea. A few get meningitis when the virus attacks the covering of the spinal cord or brain. Paralysis or weakness in the arms, legs, or both occurs in about 1 out of 200 people to 1 in 2000 people, depending on virus type.
Dan Diamond contributed to this report.