In August, MedPage Today reported on the detection of poliovirus in New York City wastewater and what that could mean for the discovery of new cases of polio. In this report, we follow up on what has happened since that time.
Following the discovery of the first case of polio in the U.S. in nearly a decade, in an unvaccinated young adult who developed paralysis, public health officials in New York began using wastewater surveillance to assess the risk of spread of poliovirus in the community.
Earlier this month, the CDC announced new plans to expand the wastewater surveillance program to more areas of the country, with the stated goal of identifying high-risk communities with low levels of vaccination against the virus. The program will last 4 months once it officially begins next year, the agency said.
"Wastewater testing can be an important tool to help us understand if poliovirus may be circulating in communities in certain circumstances," José Romero, MD, director of CDC's National Center for Immunization and Respiratory Diseases, said in a press release. "Vaccination remains the best way to prevent another case of paralytic polio, and it is critically important that people get vaccinated to protect themselves, their families, and their communities against this devastating disease."
The agency also noted that preliminary discussions are underway with the Michigan Department of Health and Human Services (MDHHS) and the Philadelphia Department of Public Health (PDPH), though local officials at these departments have emphasized that the discussions are limited at the moment.
"The CDC announcement was more to establish intent and there is not yet any firm plan in place to commence wastewater testing," the PDPH said in a statement shared with MedPage Today.
Similarly, the MDHHS said without a confirmed local case of polio, "widespread wastewater testing for poliovirus in Michigan is not indicated at this time."
Still, MDHHS has been collaborating with the CDC to identify communities with lower vaccination coverage to determine where the potential risk for transmission could be a concern.
In a statement, Michigan public health officials also pointed out that "expansion of wastewater testing in potentially vulnerable locations may also help provide insight into poliovirus risk in the U.S."
The expansion of wastewater surveillance for poliovirus is a relatively new approach to monitoring the virus in the U.S., but it has long been a tool of public health officials around the world, according to Anna Bershteyn, PhD, of New York University's Grossman School of Medicine.
Wastewater surveillance "has been in place in other parts of the world; the United States is sort of late to the game in realizing that this is important," she told MedPage Today. "In fact, the polio field has really been one of the forerunners of using wastewater to look for outbreaks and decide if we need to start pushing vaccinations more here or maybe doing additional rounds of vaccination or whatever is necessary."
The case of paralysis in the U.S. has led to a re-evaluation of how poliovirus is monitored in the U.S., but Bershteyn said that another virus has been crucial to the new interest in using wastewater surveillance: SARS-CoV-2.
She noted that the U.S. created a nationwide wastewater surveillance program to help detect outbreaks of COVID-19, and it was very successful, highlighting one example at the University of Arizona where testing the sewage outputs of each building on campus helped officials narrow down a COVID-19 outbreak to one dorm.
"If we're watching sewage in a bunch of different places for the SARS-CoV-2 virus, it doesn't cost very much more at all to be looking for other viruses," she said.
Bershteyn emphasized that wastewater surveillance for polio is especially important because the vaccine used in the U.S. can reduce how much virus people shed, but it can't stop all virus transmission, meaning that while vaccinated people are protected from the disease, unvaccinated people are still vulnerable to the virus. And since some experts have expressed doubt about the global health community's ability to eradicate the virus, wastewater surveillance could be a critical and enduring public health practice to prevent cases of paralytic polio.
"Previously, there was this notion that polio had been eliminated in the United States," Bershteyn said. "Now our eyes have been opened to the realization that polio can and is transmitting in the United States."