Bats, humans, monkeys, minks, big cats and great apes – the coronavirus can find a home in many different animals. Mice have now been added to the list of potential hosts, according to a disturbing new study.
Infected rodents pose no immediate risk to humans, even in cities like London and New York, where they are ubiquitous and undesirable residents of subway stations, basements and backyards.
Nevertheless, the finding is worrying. This, along with previous work, suggests that new mutations give the virus the ability to replicate in greater numbers of animal species, experts say.
“The virus is changing, and unfortunately it’s changing pretty quickly,” said Timothy Sheahan, a virologist at the University of North Carolina at Chapel Hill who wasn’t involved in the new study.
In the study, researchers introduced the virus into the nasal passages of laboratory mice. The form of the virus, which was first identified in Wuhan, China, can neither infect laboratory mice, nor B.1.1.7, a variant that has spread across much of Europe, the researchers found.
But B.1.351 and P1, the variants discovered in South Africa and Brazil, can replicate in rodents, said Dr. Xavier Montagutelli, veterinarian and mouse geneticist at the Pasteur Institute in Paris, who led the study. The research, which went online earlier this month, has not yet been considered for publication in a scientific journal.
The results only show that infection is possible in mice, said Dr. Montagutelli. Mice caught in the wild are not infected with the coronavirus, and so far the virus does not appear to be able to jump from human to mouse, from mouse to human, or from mouse to mouse.
“Our results underscore the need to regularly assess the biodiversity that the virus can infect, especially as new variants emerge,” said Dr. Montagutelli.
The coronavirus is believed to have emerged from bats, with another animal possibly acting as an intermediate host, and scientists fear the virus may return to what they call an animal “reservoir”.
Aside from the potential destruction of these animal populations, a coronavirus that spreads in a different species can take on dangerous mutations and return to humans in a form that current vaccines shouldn’t be able to fight off.
Minks are the only animals known to catch and return the coronavirus from humans. In early November Denmark killed 17 million farmed minks to prevent the virus from developing into dangerous new varieties in the animals.
More recently, researchers found that B.1.1.7 infections in domesticated cats and dogs can cause the pets to develop heart problems similar to those in people with Covid-19.
March 31, 2021, 2:20 p.m. ET
To establish a successful infection, the coronavirus must bind to a protein on the surface of animal cells, penetrate the cells, and use their machinery to make copies of itself. The virus must also evade early attempts by the immune system to thwart the infection.
Given all of these requirements, it is “pretty extraordinary” that the coronavirus can infect so many species, said Vincent Munster, a virologist at the National Institute for Allergies and Infectious Diseases. “Viruses usually have a more restricted host area.”
Mice are a well-known reservoir for hantaviruses, which cause a rare and fatal disease in humans. Although the coronavirus variants seem unable to jump from mice to humans, there is potential for them to spread among rodents, develop into new variants, and then reinfect humans, said Dr. Muenster.
The variants can also threaten endangered species such as black-footed ferrets. “This virus seems to be able to surprise us more than anything or any other previous virus,” said Dr. Muenster. “We have to play it safe.”
Dr. Sheahan said he was more concerned about transmission from farm animals and pets to humans than from mice.
“They don’t catch wild mice in your house and cuddle – they all stand up in their faces and share the same air space as they might with your cat or dog,” he said. “I would be more concerned about wild animals or pets that we have a closer relationship with.”
However, he and other experts said the results highlighted the need to closely monitor the virus’s rapid changes.
“It’s like a moving target – it’s crazy,” he added. “There is nothing we can do about it other than try to get people vaccinated very quickly.”