‘It was a very unusual situation’

Researchers in Colorado were stunned while analyzing how the COVID-19 virus spread from humans to animals at the Denver Zoo in 2021.

What’s happening?

A study published in the journal Nature Communications in December looked at an instance of the COVID-19 virus spreading from humans to big cats.

According to Westword, after humans initially transmitted the virus to two tigers, 11 lions and then two hyenas tested positive. While lions and hyenas lived in separate communities, none of the species had direct contact with each other.

“It was a very unusual situation to see three different species sequentially infected like this, and we really don’t know how that happened,” said Sue VandeWoude, a CSU veterinarian, virologist, and study author. “[The zoo was] taking significant precautions.”

Fortunately, the animals all made full recoveries. Researchers found, however, that the COVID-19 virus mutated while it was in the animals.

According to the study, these included certain traits that could “increase viral replication and fitness.”

That means that the version of the COVID-19 virus that existed in these animals could survive longer. Mutations can also allow viruses to transmit more easily and potentially infect more hosts.

Why is understanding viral transmission important?

Though instances of human-animal transmission are rare, people are still transmitting the COVID-19 virus today.

Investing in research on viruses can inform how vaccines, among other things, are made to keep people healthier and safer.

This isn’t the only instance of a large group of big felines becoming ill in recent years. Bird flu killed 20 big cats at a Washington wildlife sanctuary at the end of 2024. Scientists also noticed a surge in bird flu infections in cats in 2023 and 2024.

As COVID-19 continues to spread, other viruses (like strains of bird flu) threaten to jump from animals to humans. As the world gets warmer, heat can worsen symptoms of current illnesses, such as Long COVID.

Rising global temperatures are already affecting how vector-borne illnesses spread. The World Health Organization stated that vectors are organisms, like mosquitoes, that can spread illnesses from animals to humans.

Higher temperatures expand mosquitoes’ habitats, extend their breeding and survival period, and allow them to spread diseases beyond rainforests.

How can I stop viral transmission?

There are many tools you can use to stop viral transmission and curb viral mutation.

For airborne pathogens like the COVID-19 virus, masking up and cleaning the air are very effective strategies.

The NYC Department of Health and Mental Hygiene recommends wearing a high-quality mask or respirator, such as a KN95 or N95. Both masks and air purifiers can also filter out pollutants and allergens from the air you breathe.

For vector-borne illnesses, bug spray packs a punch. The Cleveland Clinic also recommends wearing protective clothing, emptying out standing water in places like gutters, and avoiding certain fragrances.

Meanwhile, plants like citronella and lavender can actually keep mosquitoes away.

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