A wastewater sample collected more than a year ago in northern Utah tested positive for poliovirus, according to a researcher, but state health officials said the results could not be replicated months later so there’s no threat to the public.
And there’s no plan to keep testing wastewater in Utah for the virus that can cause permanent and potentially fatal paralysis, even though federal authorities expanded testing after the country’s first polio case in nearly a decade surfaced in New York last summer.
“I don’t think there’s a reason to be concerned at this point,” said Dr. Leisha Nolen, state epidemiologist with the Utah Department of Health and Human Services, adding she doesn’t believe “there’s a change in the risk right now” that warrants further screening.
The samples shared with the University of Missouri for COVID-19 research came from the area served by the Bear River Health Department, Nolen said. Bear River Health Department spokeswoman Estee Hunt said it was from a Tremonton wastewater treatment facility.
Nolen said hearing about the positive result from a University of Missouri researcher last fall came as a surprise since Utah officials were not aware testing would be done for poliovirus on the sample, collected in February 2022.
Tests were conducted for poliovirus by the state on duplicates of the February sample, which were also sent to the Centers for Disease Control and Prevention, she said, but polio was not detected.
Additional testing was done on other samples, Nolen said, with the same negative result.
“There are risks,” she said, but she called it “exceedingly reassuring” that no polio was found in other samples, from January and March of 2022, as well as in new samples taken at the time the state was notified of the positive result, last October.
“All that was negative, so this is a possible one-off. I don’t think we’re ever going to know really why the university got that result. But even if it’s a true one-off, it was a very limited time period,” Nolen said, and not an “opportunity for people to continue to be exposed.”
‘A real shocker’
Marc Johnson, a microbiology professor at the University of Missouri School of Medicine, said he was surprised, too, to find poliovirus in the Utah sample obtained for his research into COVID-19 mutations.
“That was a real shocker,” Johnson told the Deseret News, adding, “We didn’t expect to find that.”
The virologist said he decided to test samples he’d received from Utah and other places for poliovirus because of the New York case confirmed in July, in an unvaccinated man living in an Orthodox Jewish community near New York City.
His case, the nation’s first since an overseas traveler returned with polio in 2013, was not travel related. Instead, the virus is believed to have been transmitted to him by someone who’d had an oral vaccine that has not been used in the U.S. since 2000.
Johnson said he and his research team were curious about how widespread polio might be and decided to come up with an assay to determine the presence of polio in wastewater, using the samples they already had on hand.
“We weren’t secretive about it,” he said, noting Utah officials were notified right away when a sample tested positive for poliovirus. “They didn’t sit on their hands. I think we had a meeting with the CDC within about a day or two.”
Johnson, who describes himself on Twitter as a “molecular virologist, professor and wastewater detective,” said it’s “not entirely true” his result could not be replicated.
“We sent our sample to the CDC and they confirmed it,” he said, calling himself “peripherally involved” in that process. “I don’t think anyone is denying that the CDC verified that my sample contained polio, but I didn’t get any kind of official documentation.”
The CDC had not responded by Monday to a request made by the Deseret News last week for comment about the testing and whether it signals a need for monitoring wastewater in the state for poliovirus, as New York and several other places are doing.
Johnson said he could not name where other wastewater samples tested for polio came from, or what the results were, without obtaining permission from the participants. Later, he said he was able to report all of the assay tests on Missouri samples were negative.
Could there be more?
The positive test in Utah was discussed in late January on the popular “This Week in Virology” podcast hosted by Vincent Racaniello, a Columbia University professor who has studied the poliovirus since the 1980s and bills himself as “Earth’s Virology Professor.”
Citing a chart of weekly polio wastewater test results from last year, Racaniello pointed out two positive results that weren’t linked to the Rockland County case, in Utah around the start of February and in New York City mid-year.
“It’s a separate introduction. It’s genetically distinct,” he said, noting the oral vaccine derived polio is “coming in from other countries because we don’t use it here. It’s not surprising. People are coming in every second, right?”
Racaniello also said it’s not clear if the two distinct cases are connected.
“Who knows the relationship between the two,” he said, adding Utah “is very under sampled, so there could be even more. Utah’s samples seem to be from the beginning of last year,” months before the nation’s first case in nearly a decade was reported.
A total of 71 of the 2,041 test results reported on the chart came from Utah, done from January through early March, and in October.
Utah was one of only five states on the chart, which was dated Jan. 9, 2023. Of the others — New York, New Jersey, Connecticut and Oregon, positive tests were reported only in New York and Utah.
Han Kim, a professor of public health at Westminster College in Salt Lake City, said it’s hard to comment on the situation without knowing more details about the research that produced the positive test result.
“I kind of understand the state’s reluctance,” Kim said, given that no further trace of poliovirus was found. “Not that I doubt this researcher, but there’s so little known about what he did and the assay he used and so on.”
That raises the question of whether the result was a false positive, he said, suggesting that’s probably the conclusion reached by the state and the CDC. “In which case, do you want to get people freaked out about polio and further tests? I can see deciding no.”
Why the positive test wasn’t made public
The Bear River Health Department is comfortable with how the state responded, said Hunt, the department’s spokeswoman. She said the positive polio test was not made public after the local health department learned about it in mid-October.
“We didn’t see this as a risk to the community at all. There’s a high polio vaccination rate in that area and excellent sewage treatment so the Bear River Health Department is very confident that there is no risk to the public or there was a risk to the public,” Hunt said.
She said the CDC has tested multiple samples since the single sample was positive.
“We did not want to cause panic,” Hunt said, adding she “never felt like there was a threat to the public. Had we seen a positive result in October, then yes, definitely, we would have been notifying everyone.”
Just two months before Utah public health officials learned of the positive polio test, Nolen had said the state was “definitely discussing” starting to monitor wastewater for polio in addition to COVID-19.
The state’s epidemiologist said then it would be “useful to know if there’s polio in our community that could get into people and cause disease,” especially since vaccination rates have dropped due to the COVID-19 pandemic.
But Nolen said she’s changed her mind after extensive discussions with the CDC. She said the federal agency advised the state not to routinely test wastewater for polio unless someone is diagnosed here with the virus.
“One of our roles as public health officials is not to overly alarm our population. We want to be honest. We want to get information out,” Nolen said. “But we also don’t want to cause alarm.”