Scientists are concerned about the spread of COVID-19 in animals and what it may signal for future pandemics.

Many wild animals, including white-tailed deer and minks, can spread the disease among themselves. Animals in zoos across the U.S. have contracted and even died from the virus, and there have also been reports of household pets around the world contracting the virus. While the virus likely developed into the well-known strains today in humans, and humans continue to be the main transmitters, the possibility of the virus mutating in animals and then the animals transmitting the virus back to humans, with a more deadly variant, is a concern.

However, it is more likely that humans passed the virus to animals in zoos or to wild animals, according to CNN. Dr. Surech Kuchipudi of the Animal Diagnostic Laboratory at Pennsylvania State University said pollution is a likely explanation for how many animals got the virus.

Thrown-out items like masks and tissues or even sewage, which is known to spread the virus, easily make their way to animal populations even when there is not a deadly pandemic. 

As humans also continue to encroach on wild areas, it is more likely pandemics will continue to result from rare wild animal to human transmission.

As for COVID-19, the consensus is that the virus came from bats, who then gave it to another animal before it passed to humans. The first outbreak of the virus in Wuhan, China gained national attention for wet markets that are home to many wild animals where a virus could easily develop.

However, it is important to note that there is not a consensus on how or where the virus got from animals to humans. Some suspect the virus came not from animals at all, but from a lab in China, intentionally or accidentally.