How many animal species have caught COVID? First global tracker has (partial) answers

Mink get it. Hamsters get it. Cats and dogs get it.

They're a few of the many animal species to have contracted COVID-19.

But how many species have been affected? And how many cases have there been in the animal kingdom?

Those are difficult questions to answer – just as it's hard to come up with an accurate total for human cases, since many people don't report a positive test to health authorities. Yet it's an important task, say researchers, because of the possibility that the virus could mutate into a perhaps more transmissible or virulent strain in animals and then pass back to humans.

Now there's a first effort at compiling a global database of animal counts. Amélie Desvars-Larrive, professor at the University of Veterinary Medicine Vienna, and her team of Austrian researchers combed the internet for data from official sources. On July 23, her team in collaboration with the Wildlife Conservation society published the first COVID data tracking dashboard for cases in animals in Scientific Data.

It's preliminary — but still helpful

The interactive visualization lets users explore which animals have gotten COVID, how many cases were reported for each species and the source of the data. It also covers what happened to the animals, ranging from mild symptoms like a runny nose to more severe symptoms like myocarditis or even sudden death.

The number of cases reported are undercounts, since there's no systematic gathering of information across countries, among other reasons. But scientists say it is a welcome addition to the body of COVID data.

"[COVID surveillance in animals] has been through either activities at a governmental level or through independent research," says Meghan Davis, professor of environmental health at Johns Hopkins, who was not involved in the study. "What these authors did very well was identifying some of the most likely sources of data and then pulling this information together into a graphical interface.

"This dashboard is incredibly useful at communicating information and bringing together data from multiple sources. People who make public health decisions or are interested in this topic can now interact with the data without needing to go to all of these different sources," says Davis.

"What was new to me was to see [how the number of COVID infections] in the different species compared," says Wim van der Poel, veterinarian and professor of zoonotic viruses at Wageningen University in the Netherlands. Van der Poel was acknowledged in the paper but not involved in the study.

And the limitations of the tracker might help highlight where better reporting or testing initiatives on COVID in animals are needed. "[The dashboard] shows us where we may need to increase our activities," says Davis. "It's really showed me where we have surveillance gaps or lack of reporting."

The study authors acknowledge the gaps.

For example, comparing case counts from country to country isn't useful for understanding which countries have the most cases in animals because "low- and middle-income countries cannot search for COVID in animals as they need to target resources for testing to humans," says Desvars-Larrive.

The statistics about death rates are likely overestimates due to the high number of unreported asymptomatic cases. "The reported cases are only the tip of the iceberg and the symptomatic ones are the tip of the tip of the iceberg," says Desvars-Larrive. "The data don't show the true mortality rate. I think the case fatality rate in animal is low, actually."

How many animals, how many species?

The dashboard has so far collected 704 cases of COVID in animals from the Program for Monitoring Emerging Diseases and the World Animal Health Information System. There are 27 different species cited from 39 different countries. Those cases are typically confirmed through a PCR test.

The most confirmed cases are in mink, with 187 cases, followed closely by cats and dogs with 177 and 160 confirmed cases respectively. More often than not, the CDC theorizes that those cats and dogs got COVID from their owners, even though there hasn't been a large study confirming that theory.

They caught it from us. Can they infect us as well?

The question that looms over this enterprise: Can animals pass COVID back to humans?

In late 2020, an outbreak of COVID in mink fur farms resulted in some of the caretakers contracting the virus and ultimately led Denmark to cull 17 million of the animals. And late last year COVID infections transmitted from hamsters to people sparked an outbreak in Hong Kong.

The cases of COVID transmission from minks and hamsters both happened in situations where people were caretakers for a large number of animals. But just last month, the first evidence of COVID being passed from a cat to a person was reported. According to a study published last month in Emerging Infectious Diseases, the cat sneezed in the face of a veterinary surgeon who was testing the animal for COVID. Three days later the vet tested positive for COVID, but none of the vet's close contacts did, suggesting the vet got the virus from the infected cat.

There's also a concern that wildlife infected with COVID — like a population of deer in Pennsylvania and other parts of North America — could become reservoirs for the virus, meaning the virus can circulate in them, perhaps even mutate into more transmissible or virulent strains and get passed back to humans. "That could mean that there is a continuing risk from those animals for public health," says van der Poel. "But we have not seen [evidence of a wildlife animal reservoir] yet."

Scientists still don't know how those deer got COVID. It's unlikely the deer caught it from direct contact with humans, though transmission from contaminated wastewater or other infected animals, like feral cats, are possibilities.

As for the risk of pets and other animals transmitting the virus to humans? "I don't think that there is that is that is a major risk," says van der Poel. The CDC agrees that the risk of catching COVID from an animal is very low. Says van der Poel: "The risk to contract COVID from other people is far higher than from an animal."