GRAMGenetic 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 detected in Jerusalem and London, the Global Polio Eradication Initiative announced Friday.
“Further research, both genetic and epidemiological, is 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, indicating a silent spread of vaccine-derived polioviruses over a wide geographic area.
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“It basically suggests that there has been 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 living in Rockland County, New York, recently developed paralysis that was diagnosed as being caused by a type 2 polio vaccine virus. Rockland County Health Officials , which is north of New York City, said the man had not traveled outside the country at the time he would have been infected. That means someone else had to have brought the viruses into the country.
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Vaccine-derived polioviruses (VDPV in polio parlance) come from the oral polio vaccine, which contains live but weakened poliovirus. Children vaccinated with this vaccine excrete the vaccine viruses in their feces. In places where hygiene is poor, these viruses can spread from one child to another, immunizing others as they do so. But as they spread, the vaccine viruses may regain the power to paralyze. At this point, more children worldwide are paralyzed each year by circulating vaccine-derived polioviruses than by wild-type viruses, which are now only endemic 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 used exclusively inactivated polio vaccine, which contains no 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, which means that this chain of transmission began in another country, currently unidentified.
The type 2 component of the oral vaccine was withdrawn in 2016 in a coordinated global effort to try to stop the transmission of type 2 vaccine viruses. But the move, known as “the switch,” was unsuccessful. Until recently, when outbreaks of the type 2 vaccinia virus 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 with fire.
It must be from one of these campaigns that type 2 viruses originated in this chain of transmission.
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 county man got there. from Rockland.
The Jerusalem and London viruses were detected in sewage samples. To date, no cases of paralytic polio associated with this chain of transmission have been reported in either location.
Oberste pointed out that the three places – Jerusalem, London and New York – attract a large number of travelers.
“Clearly they are related. Directionality is difficult to infer, especially when you only have a small number of sequences,” she said. “It’s going to be hard to say: Was it someone who came from Israel directly to New York? Someone who came from London directly to New York? Or even someone who brought it to Israel from somewhere else and it was brought to New York by someone who is from wherever that place is, but it was the same virus?
While the finding 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-gone threat need to make sure vaccination rates stay high. and vigilantes, the polio program said. said.
“It is vital that all countries, particularly 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 rapid response,” the statement said.
The Global Polio Eradication Program is a partnership of the World Health Organization, the CDC, the United Nations Children’s Fund (UNICEF), the Rotary International service club, and the Bill & Melinda Gates Foundation.
Source: www.statnews.com