Study: COVID Variant in NYC Sewage Could Be Caused by Rats

The variant of COVID-19 found in New York City sewage last year could have originated in the city's rat population, according to a new study published in Nature Communications earlier this month.

The study, co-authored by University of Missouri virologist Marc C. Johnson, found that the amino acid changes detected in the new variant "has not been seen in patients. Ever. But this amino acid change has been seen in rodent-adapted virus," Johnson told Curbed.

"In immunocompromised patients, you see a lot of similar mutations, but this one particular mutation right at the receptor-binding site has just not been found," he added. "If these lineages are coming from an immunocompromised patient, it is probably that, a single patient, and it's really hard to believe that this much signal could come from one person."

Johnson noted that the "alpha, beta, and gamma" strains of COVID-19 "have gained the ability to infect rodents, but the original strain of COVID could not."

When asked why the authors specified rats as a possible source, Johnson said, "There was a figure in the paper where we actually show that these lineages have all gained the ability to utilize the rat receptor. It was this suspicion that led us to do the experiment that confirmed this: I was like, 'Well, probably not rats, but if it is rats, then it should have gained the ability to infect rat cells,' and sure enough, the virus did."

However, he did note that scientists have yet to uncover evidence that COVID-19 is widely circulating among rats.

"I think the important thing to keep in mind here is that every time the virus replicates, it has a possibility to mutate," said another of the study's co-authors, Monica Trujillo, a microbiologist at Queensborough Community College. "So if there is a population where you are not aware where the virus is replicating, that is worrisome. That is why it's important to know where these cryptic sequences are coming from."

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