Polio case in US linked to viruses detected in UK and Israel, suggesting silent spread

gGenetic analysis of the virus responsible for the first case of polio in the United States in nearly a decade shows it is linked to vaccine-derived viruses recently detected in Jerusalem and London, the Global Initiative for the eradication of poliomyelitis.

“Further investigations – both genetic and epidemiological – are underway to determine the possible spread of the virus and the potential risk associated with these various isolates detected in different locations around the world,” the program said in a statement.

The analysis indicated that the viruses have been circulating for some time, signaling a silent spread of vaccine-derived polioviruses over a wide geographic area.

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“It basically suggests that there was substantial, undetected transmission,” Walter Orenstein, a polio expert at Emory University who was not involved in the analysis, told STAT.

The case, an unvaccinated man in his 20s who lives in Rockland County, NY, recently developed paralysis that was diagnosed as having been caused by a type 2 polio vaccine virus. Rockland, upstate New York, said the man had not traveled outside the country when he was believed to have been infected. This means that someone else must have brought the viruses into the country.

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Vaccine-derived polioviruses – VDPVs in polio jargon – come from the oral polio vaccine, which contains live but weakened polioviruses. Children who are immunized with this vaccine excrete the vaccine viruses in their stools. In places with poor hygiene, these viruses can spread from child to child, immunizing others as they do. But as they spread, vaccine viruses can regain the power to paralyze. At this point, more children worldwide are crippled each year by circulating vaccine-derived polioviruses than by wild-type viruses, which are now endemic only in Afghanistan and Pakistan.

Due to the risk associated with the oral vaccine, the United States stopped using it in 2000; since then it has exclusively used the inactivated poliomyelitis vaccine, which does not contain live virus. The UK also uses IPV, as it is called.

Israel uses both OPV and IPV. But the version of the oral vaccine he uses does not include type 2 viruses, meaning this chain of transmission started in another country, currently unidentified.

The type 2 component of the oral vaccine was removed in 2016 as part of a coordinated global effort to try to stop the transmission of type 2 vaccine viruses. But the move, known as “the switch” , did not succeed. Until recently, when outbreaks of vaccine virus type 2 occurred, the response was to use an oral vaccine containing only the type 2 strain to try to stop the spread – a fire-fighting approach. .

It is certainly from one of these campaigns that the type 2 viruses in this chain of transmission originated.

Steve Oberste, chief of the polio and picornavirus branch at the Centers for Disease Control and Prevention, said it is impossible with the information currently available to determine where the chain of transmission began or how the viruses that infected the man from Rockland County have achieved it.

The Jerusalem and London viruses were detected in sewage sampling. To date, no cases of paralytic poliomyelitis associated with this chain of transmission have been reported in either location.

Oberste noted that the three locations – Jerusalem, London and New York – attract a large number of travelers.

“Clearly they are related. It’s hard to infer directionality, especially when you only have a small number of sequences,” he said. “It will be difficult to say: is it someone who came from Israel directly to New York? Someone who came from London straight to New York? Or even someone who brought him to Israel from somewhere else and was brought to New York by someone from anywhere, but it was the same virus? »

While the discovery doesn’t help solve the mystery of how the Rockland County man contracted polio, it does underscore that countries that thought polio was a long-lost threat need to ensure that Immunization rates remain high and they remain vigilant, the polio program said.

“It is vital that all countries, especially those with a high volume of travel and contact with polio-affected countries and areas, strengthen surveillance to rapidly detect any new virus importation and facilitate a response. fast,” the statement said.

The Global Polio Eradication Program is a partnership between the World Health Organization, CDC, United Nations Children’s Fund (UNICEF), service club Rotary International, and the Bill & Melinda Gates Foundation.


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