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Researchers find COVID-19 in New York sewer rats

They say the potential risk of COVID transmission between urban rats and humans highlights the need for continued monitoring.

November 26, 2022 6:38pm

Updated: November 27, 2022 11:43am

Researchers have found signs of the COVID-19 virus among New York City’s massive rat population, meaning they may be the source of strange coronavirus mutations found in the city’s wastewater last year.

A new study from the University of Minnesota and the USDA found that about 16% of rats they studied had antibodies to COVID, indicating they had been exposed to the virus, reports the New York Post.

“We were concerned that there was a possibility that we were going to find a spillover event knowing that [COVID-19] had been detected in some other animal species,” Dr. Julianna Lenoch, national coordinator of the USDA-APHIS Center and co-author of the paper, told The Post.

The coronavirus strain that sparked the pandemic, SARS-CoV-2, is most similar to viruses found in bats. However, the National Park Service bats are often misclassified as rodents but are, in fact, more closely related to primates and humans.

“Over the last two and a half years we found [the virus] moved from humans to new animal populations,” Lenoch added, pointing to white-tail deer and minks.

Public health experts have turned to sewage to gauge the level of coronavirus in an area, which they can regularly test for levels of COVID shed in human feces.

Furthermore, wastewater analysis can also be used to trace and forecast mutations of the virus, seen in how Wisconsin researchers were able to trace a unique mutation from the city’s wastewater back to a single building with six restrooms.

Attention turned to the Big Apple’s sewer rats after researchers from the University of Minnesota and CUNY’s Queens and Queensborough colleges found a series of mysterious never-before-seen mutations of COVID in their wastewater studies last year, some of which contained rat DNA.

Researchers captured almost 80 Norwegian rats in late 2021 and found that 16.5% had antibodies for the virus. When they administered PCR tests on the lungs of captured rats, only 5% tested positive. Partial genomes of SARS-CoV-2 were extracted from four rats in the study.

Through a “virus challenge study,” the team found that Sprague Dawley rats, another species commonly used in scientific research, could be infected by the Alpha, Delta and Omicron variants of COVID-19 – showing the potential for transmission.

The paper was released publicly on Monday but has not yet been peer-reviewed.

Its authors said their findings highlight the potential risk of “zoonotic transmission,” between urban rats and humans, of COVID and “the need for further monitoring of SARS-CoV-2 in those populations.”