GGenetic analysis of the virus responsible for the first case of polio in the United States in nearly a decade shows it is related to vaccine-derived viruses recently found in Jerusalem and London, the Global Polio Eradication Initiative said Friday.
“Further studies – both genetic and epidemiological – are ongoing to determine the spread of the virus and the potential risks associated with these different isolates found in different locations around the world,” the program said in a statement.
The analysis showed that the viruses had been circulating for some time, implying the silent spread of vaccine-derived polioviruses over a wide geographic area.
“Essentially, this suggests that a serious infectious disease is being missed,” Walter Orenstein, a polio expert at Emory University who was not involved in the analysis, told STAT.
In this case, an unvaccinated man in his 20s living in Rockland County, New York developed paralysis diagnosed as caused by the type 2 poliomyelitis vaccine virus. Health authorities in upstate New York’s Rockland County said the man had not traveled out of the country at the time of the infection. This means that someone else has to bring the viruses into the country.
Vaccine-derived polioviruses—VDPV in polio parlance—come from the polio vaccine, which contains live but weakened polioviruses. Children vaccinated with this vaccine excrete vaccine viruses in their feces. In areas with poor hygiene, these viruses can be transmitted from child to child, which immunizes others. But as they spread, vaccine viruses have the ability to paralyze again. Vaccine-derived polioviruses paralyze more children worldwide each year than wild-type viruses, which are currently endemic only in Afghanistan and Pakistan.
Because of the risks associated with the oral vaccine, the United States stopped using it in 2000; Since then, he has used only the inactivated polio vaccine, which does not contain live viruses. The UK also uses what is called BTI.
Israel uses both OPV and IPV. But the version of the oral vaccine he used does not contain the type 2 virus, meaning the chain of transmission began in another, currently unknown country.
The type 2 component of the oral vaccine was removed in 2016 in a coordinated global effort to stop transmission of type 2 vaccinia viruses. But the so-called “transition” move did not succeed. Until recently, when a type 2 vaccinia virus emerged, an oral vaccine containing the type 2 strain had to be used to try to stop its spread – firefighting.
Type 2 viruses in this transmission chain must originate from one of these campaigns.
Steve Oberst, director of the polio and picornavirus division at the Centers for Disease Control and Prevention, said it’s currently not possible to determine exactly where the chain of transmission began or how the virus reached the person in Rockland County.
Viruses from Jerusalem and London were found in sewage samples. To date, there have been no cases of paralysis associated with this chain of transmission.
As Oberste notes, all three locations – Jerusalem, London and New York – attract large numbers of travelers.
“They are clearly connected. “It’s hard to infer directionality, especially when you have a small number of sequences,” he said. “It’s going to be hard to say: Is it someone who came directly from Israel to New York? Someone who came directly to New York from London? Or was it brought to Israel from somewhere else and someone brought it to New York from there, but was it the same virus?
While the finding doesn’t help solve the mystery of how the man in Rockland County became paralyzed, it underscores the need for countries that have long thought polio to be dangerous, with high vaccination rates and vigilance. said.
“It is critical that all countries, particularly those with high levels of travel and contact with polio-affected areas, step up surveillance to rapidly detect any new importation of the virus and facilitate a rapid response,” the statement said.
The Global Polio Eradication Program is a partnership between the World Health Organization, the CDC, the United Nations Children’s Fund (UNICEF), the Rotary International Service Club, and the Bill and Melinda Gates Foundation.