Public health officials have made a major discovery in the international hunt for a case of polio that paralyzed a New York man: The virus that infected him matches the genetic fingerprint of polioviruses found in sewage samples from London and Jerusalem. Officials from the Centers for Disease Control and Prevention and the World Health Organization told ProPublica on Friday.
It is still unclear how the virus moved from one place to another and where it first appeared.
“This is still under investigation,” Oliver Rosenbauer, liaison officer for the WHO Global Polio Eradication Initiative, said in an email.
Searching for answers thousands of miles away shows how viruses can spread around the world. Polio is highly contagious, and since most infections cause no symptoms, it can spread silently through unmonitored communities.
ProPublica reported Tuesday that U.S. public health agencies have generally failed to test sewage for evidence of polio, relying on high vaccination rates to protect Americans from the disease, but there are signs of cracks in that shield both here and abroad.
Public health experts say waiting for patients to develop symptoms can be dangerous: 1 in 100 to 1,000 infections can occur in a case of paralysis. New York’s health officials started only after the sewage was tested.
The New York incident was the first in the US in almost a decade. It was discovered after a young man in Rockland County, in northwestern New York, sought medical attention in June for weakness and paralysis. He was not vaccinated against poliomyelitis. It was only in July when tests confirmed that he had polio.
Genetic sequencing confirmed that he had contracted polio from the vaccine. This type of polio has been linked to the oral polio vaccine, which has not been used in the US since 2000. The oral vaccine, which is still used in other parts of the world, relies on weakened polio viruses to activate the immune system and generate protective antibodies. In rare cases, when weakened viruses circulate in unvaccinated or unimmunized people, they can revert to a form that can make unvaccinated people sick.
Public health officials said in early June that traces of the poliovirus found in sewage samples from Rockland County and Jerusalem were still too weak to cause paralysis. It’s unclear where the virus originated, strong enough to make a patient in Rockland County sick.
A spokeswoman for the Rockland County Health Department said she could not confirm whether the man had traveled to London or Jerusalem this year.
Another mystery is that the United Kingdom, like the United States, did not use the polio vaccine for many years. Instead, both use only an injectable vaccine that contains inactivated viruses and does not cause vaccine-derived polio. Although Israel uses an oral polio vaccine, its version does not contain the type 2 strain of polio that was found in sewage samples or was infected in New York.
New York City officials are now testing both stored sewage samples collected as part of their efforts to track COVID-19 and recent samples for signs of polio.
Although high vaccination rates in the United States make polio less dangerous, some communities have much lower vaccination rates than the nation as a whole. In 2018 and 2019, Rockland County grappled with a prolonged measles outbreak — preventable by vaccination — concentrated in its Orthodox Jewish community. Some news organizations reported that the paralyzed man was a member of that community.
Most Americans are not old enough to remember, but during the first half of the 20th century, polio was one of the nation’s most feared diseases. It mainly affects young children, attacking their spinal cord, brain stem, or both, leaving thousands with irreversible paralysis. After the first vaccine was approved in 1955, cases in the United States declined dramatically within a few years.