The US will expand polio sewage monitoring to include communities with low immunization rates outside the New York City metro area after a summer outbreak paralyzed an unvaccinated adult and raised questions about how widely the virus could circulate.
The Centers for Disease Control and Prevention said in a statement Wednesday they would first work with health officials in Michigan and Philadelphia to identify communities with low immunization rates and begin testing wastewater in those areas. The CDC said it is in preliminary discussions with other state and local health officials about expanding testing to other areas of the United States
Federal health officials will also extend wastewater surveillance for polio to counties that have possible links to communities in New York where the virus is known to circulate. The CDC said the expanded surveillance program will help determine if the poliovirus is present in other parts of the United States and guide efforts to increase immunization rates in at-risk communities.
The wastewater tests last at least four months after they begin. The CDC described the expanded surveillance program as strategic and limited in focus to certain vulnerable communities.
Federal health officials’ decision to expand polio surveillance comes after an unvaccinated adult in Rockland County, New York, became paralyzed after contracting the virus over the summer. The CDC considers a single case of paralysis from polio to be a public health emergency because it is so rare and indicates the virus is spreading throughout the community.
Public health officials then confirmed that the virus was indeed spreading widely after sewage samples from five other New York boroughs tested positive. The Rockland patient has not traveled internationally, meaning he almost certainly picked up the virus from someone else in the community.
The virus, which is spreading in the New York area, is related to a strain used in the oral polio vaccine. The US stopped using this vaccine more than 20 years ago because it uses a live but weakened virus that can, on rare occasions, mutate and become virulent again, posing a threat to the unvaccinated.
Other countries still use the oral polio vaccine because it’s cheap, effective, easy to administer, and generally safe. The US uses an inactivated polio vaccine that is given as a series of shots. It uses killed viruses that cannot replicate or mutate.
Although the Rockland County patient is believed to have contracted polio through local spread, the chain of transmission likely came from someone overseas who received the oral vaccine.
The CDC said the risk to the general public is low because more than 92% of Americans are vaccinated against polio. The vaccine is very effective in preventing serious illness and paralysis, but it does not prevent transmission of the virus.
The oral vaccine is very effective at blocking transmission and is usually used to suppress outbreaks. The CDC is in talks about potentially introducing a newer version of the oral vaccine that’s more stable and has a lower risk of mutations to help tackle rare outbreaks like the one in New York.
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