While editing this month’s Clinical Issues article, “Plague take it! What’s new in viral infectious diseases?” the Centers for Disease Control and Prevention (CDC) announced that it will be expanding efforts to test wastewater in the Philadelphia and Detroit areas, and that preliminary discussions with other selected state and local health departments are underway for testing. This follows confirmation of a case of paralytic polio in Rockland County, New York this past summer in an unvaccinated young adult. Wastewater samples, which were originally collected for SARS-CoV-2 surveillance, were linked to the type 2 vaccine-derived poliovirus. Before this summer, polio was not on the top of many people’s minds. This patient was only the second identification of community transmission of poliovirus in the United States since 1979; the previous instance, in 2005, was an Amish infant that was hospitalized with type 1 vaccine-derived poliovirus in Minnesota.
The CDC stated, “Even a single case of paralytic polio represents a public health emergency in the United States.”1 The reasons being that polio has potentially severe consequences and low vaccination coverage in the patient’s county of residence indicates that the community is at risk for additional cases of paralytic polio. As of December 5th, sequencing analysis by the CDC confirmed the presence of poliovirus in a total of 94 positive samples of concern taken from Rockland and surrounding counties. Of the 94 positive samples of concern, 87 samples were found to be genetically linked to the individual case of paralytic polio in the Rockland County patient.2
There are two types of polio vaccines. The inactivated polio vaccine creates antibodies that enter the central nervous system and must be administered through injection by a trained health worker. The oral polio vaccine, which contains a weakened form of the virus, triggers the immune system to create antibodies to fight off the disease. The oral vaccine is effective but in rare cases can mutate and cause vaccine-derived poliovirus. The oral polio vaccine has not been used in the United States since 2000 because of that risk.
Most Americans are vaccinated for polio as children. However, there are pockets of the population that have not been vaccinated. Those who are unvaccinated or incompletely vaccinated are at risk of contracting and spreading polio. According to the CDC press release, poliovirus wastewater testing is not routinely or broadly recommended, and there are strict laboratory safety requirements. However, the strategic use of wastewater testing in a limited number of at-risk communities can help determine if poliovirus is present in other parts of the United States outside the areas tested following the New York case and can be used to target vaccination efforts to rapidly improve local polio vaccination coverage if needed. Over the next few months, the CDC-led wastewater testing will inform vulnerable communities whether there are positive wastewater detections and hopefully improve vaccination rates in these communities.
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REFERENCES
- Link-Gelles R, Lutterloh E, Schnabel Ruppert P, et al. Public Health response to a case of paralytic poliomyelitis in an unvaccinated person and detection of Poliovirus in wastewater - New York, June-August 2022. MMWR Morb Mortal Wkly Rep. 2022;71(33):1065-1068. doi:10.15585/mmwr.mm7133e2.
- Polio wastewater surveillance. Health.ny.gov. Accessed December 5, 2022. https://health.ny.gov/diseases/communicable/polio/wastewater.htm.
