How polio came back to New York for the first time in decades, silently spread and left a patient paralyzed - CNBC

How polio reemerged in New York this year remains the subject of investigation, but public health officials believe the virus originated overseas in a country that still uses the oral polio vaccine.

Genetic analysis of New York poliovirus samples indicates a weakened virus strain used in one of the oral vaccines mutated over time to cause the outbreak.

"The underlying lesson is this is an infectious disease and it travels easily with population movements," said Oliver Rosenbauer, a spokesperson for the Global Polio Eradication Initiative, the organization that represents the worldwide campaign to eliminate the virus.

The oral polio vaccines are generally safe, effective, cheap and easy to administer.

Although recently immunized people can pass the oral vaccine virus on to others for a few weeks, it's not normally a problem because the strain is weakened so it does not cause disease, Rosenbauer said.

And when people who are not immunized catch the mutated vaccine-derived virus, they can become paralyzed, like the patient in Rockland County.

The inactivated polio vaccine is very effective at preventing disease, but it does not stop transmission of the virus.

This means that although people immunized in New York with the inactivated polio vaccine are protected against disease, they can still catch and spread the strain that mutated from the oral vaccine.

After the Rockland County patient developed paralysis, health officials in New York used wastewater surveillance developed during Covid to test sewage samples.

Poliovirus was detected in Rockland County, then in neighboring Orange County, New York City, Sullivan County and later in Nassau County on Long Island.

While the Rockland County adult hadn't traveled internationally, they attended a large gathering eight days before they started experiencing symptoms, which suggests that they had contracted the virus from someone else in the community, Schnabel Ruppert said.

The Rockland County health commissioner said she's very concerned another unvaccinated person in the community could contract paralytic polio.

The viruses in all three countries are related to the weakened Sabin Type 2 virus used in one of the oral polio vaccines.

The U.K., like the U.S., does not use oral vaccines at all, and Israel does not use oral vaccines containing the Sabin Type 2 strain, according to the initiative.

And the poliovirus samples from the three countries are not linked to known vaccine-derived polio virus outbreaks in other countries, such as the Democratic Republic of the Congo, Nigeria, Somalia and Yemen, Rosenbauer said.

The CDC, in a statement, said although the Rockland County patient did not travel to a country where vaccine-derived virus is present, it's possible others in the individual's community may have visited such a place or a visitor brought it into the U.S.

Steve Oberste, who heads the CDC's polio lab, said genetic analysis of the sample from the Rockland patient indicates the virus is about a year old.

Dozens of countries around the world — primarily in Africa, the Middle East and South Asia — are still using oral vaccines that contain the Sabin Type 2 strain.

The vaccine virus is the same in every vial, so there's no identifying feature on it that would allow scientists to trace wastewater specimens found in New York back to a specific country that still uses the oral vaccine containing the Sabin Type 2 strain, Oberste said.

Health authorities in New York, Israel and the United Kingdom have all responded swiftly to prevent an explosive outbreak of polio like the one in the Netherlands 30 years ago, Rosenbauer said.

The goal of the Global Polio Eradication Initiative is to switch the world to the inactivated vaccine once the oral vaccine has stamped out the remaining wild type poliovirus.

The oral polio vaccine is needed to eradicate wild type virus from the world, but it also carries the risk of mutating into a virulent form.

And when vaccine-derived virus outbreaks happen, the oral vaccine is used to stop them — even in countries that rely on the inactivated vaccines for routine immunization, according to the CDC.

In Rockland County, more than 6,400 doses of the inactivated vaccine have been administered so far this year and about 64% were given in the two ZIP codes with the lowest immunization rates for kids under age two, Schnabel Ruppert said.

Rosenbauer said the question is whether immunization campaigns with the inactivated vaccines in New York and London are enough or whether the oral vaccine might need to be temporarily reintroduced to break the chain of transmission.