The US now meets the criteria to enter the World Health Organization's (WHO) list of countries where circulating vaccine-derived poliovirus (cVDPVs) have been identified and are in circulation, the CDC announced on Tuesday. This is due to an ongoing outbreak in Rockland County, New York state, and surrounding areas. Joining them on the watchlist are around 30 other countries, including the UK, Ukraine, Israel, Yemen, and a large number of low- and middle-income counties in Africa.
It all started in July 2022, when an unvaccinated person in Rockland County became the first confirmed polio case in the US since 2013. Following probing from the CDC, poliovirus was then detected in Rockland Country sewer water samples dating back to June 2022, indicating this single case was just the tip of the iceberg.
Now the virus has been detected in an individual and an environmental sample, the US meets the WHO’s definition of a country with circulating cVDPV.
Polio is a highly infectious viral disease that can affect the nervous system and cause muscle weakness, largely affecting children under 5 years of age. Although a huge threat to the population just decades ago, the disease is now preventable thanks to a safe and effective vaccine (which doesn’t include the weakened virus found in the oral polio vaccine).
The strain of the virus is type 2 VDPV (vaccine-derived poliovirus). These polioviruses are related to a weakened form of the virus used in some older forms of the oral polio vaccine. This weakened form of the virus can evolve over time and behave more like the naturally occurring virus, meaning it can potentially infect the unvaccinated.
However, this oral polio vaccine has not been used in the US for decades, suggesting the cases were likely imported from elsewhere in the world where this vaccine type is still used. It's also notable that Rockland Country has a relatively low vaccination rate compared to the rest of the US.
The CDC stressed that cVDPVs are not caused by a child receiving the polio vaccine and that vaccination remains the best way to provide this disease.
“Polio vaccination is the safest and best way to fight this debilitating disease and it is imperative that people in these communities who are unvaccinated get up to date on polio vaccination right away,” Dr José R. Romero, Director of CDC’s National Center for Immunization and Respiratory Diseases, said in a statement.
“We cannot emphasize enough that polio is a dangerous disease for which there is no cure,” Dr Romero emphasized