Scientists discovered that rats in New York City were infected with SARS-CoV-2 during the pandemic and are susceptible to the Alpha, Delta, and Omicron variants.
Scientists have known for some time that SARS-CoV-2 —the virus that causes COVID-19 — can infect animals and be transmitted between humans and animals. For example, the CDC says cats, dogs, hamsters, and ferrets, have been infected with SARS-CoV-2. In addition to our domesticated furry friends, animals such as deer, mink, big cats, and even hippopotamuses and manatees have been infected.
Of these, the only documented cases of an animal spreading COVID-19 to humans involved mink on mink farms, a white-tailed deer in Canada, pet hamsters in China, and a cat in Thailand. However, in 2021, an African lion infected with the virus transmitted it to his human caregiver at a zoo. This case was the first zoo animal-to-human transmission of SARS-CoV-2 recorded by scientists.
Animal-to-human transmission of disease, or zoonosis, is highly concerning for scientists and health officials, as three out of four new or emerging infectious diseases in people come from animals. This makes understanding the pathways of zoonotic disease critical.
Recently, a study published online in the American Society for Microbiology’s journal, mBio, found evidence that wild rats can become infected with Alpha, Delta, and Omicron variants of SARS-CoV-2. The scientists who conducted the research also found that rats in New York City occupying sewer systems and other areas in the city were exposed to the virus during the COVID-19 pandemic.
Because wild rats are so prevalent in large urban areas, and they have the potential to spread disease, scientists wanted to determine if the rodents were infected with the virus that causes COVID-19 and, if so, which variants they had.
To do this, the researchers captured 79 wild Norway rats in New York City during the fall of 2021 and tested them for SARS-CoV-2.
The results showed that 13 of the 79 rodents tested IgG- or IgM-positive for the virus. In addition, further testing revealed that rats could become infected with the Alpha, Delta, and Omicron variants. The team also found that the Delta variant resulted in the highest infectivity.
"Our findings highlight the need for further monitoring of SARS-CoV-2 in urban rat populations and for evaluating the potential risk of secondary zoonotic transmission from these rat populations back to humans," the study authors wrote.
What diseases come from rats?
History has proven that rats can transmit disease to humans, even indirectly. The most notorious example was the bubonic plague, or the 'Black Death,' which killed millions of people in Europe during the 14th century. This disease was associated with rodents infested with plague-carrying fleas. However, the bacteria infection that caused the plague is curable with modern antibiotics.
Other diseases carried by wild rodents such as rats include monkeypox, hantavirus, salmonella, and others. Therefore, the CDC recommends controlling rodent infestations in homes to reduce the risk of exposure to rat-borne illnesses.
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