Introduction

As the COVID-19 pandemic evolves, scientists continue to investigate its impacts on various species, revealing troubling discoveries. Researchers have detected coronavirus infections in pets like cats and dogs, alongside exotic zoo animals, including big cats and gorillas, even under strict safety protocols.

The situation became more worrisome in December when the USDA confirmed the first case of SARS-CoV-2, the virus responsible for COVID-19, in a wild animal—a mink found in Utah near a farm grappling with its own outbreak. This raised significant concerns: Are humans inadvertently transmitting this deadly virus to local wildlife? What could this mean for the future of both wild animals and human health?

How Viruses Cross Species: The Science Behind Spillover

As experts who study viral transmission in wildlife, we are currently investigating the potential for human-to-wildlife spillover of SARS-CoV-2. The scientific term for when a virus jumps to a new species is "spillover." While this phenomenon is formidable, it does not occur easily—for successful transmission, a virus must bind to a specific cell protein and infiltrate the cell while evading that species' immune responses.

Notably, closely related species have a higher chance of sharing viruses. For instance, gorillas were recently confirmed infected with SARS-CoV-2, indicating a worrying likelihood of transmission between humans and their primate relatives. While some viruses remain species-specific, others, like influenza and coronaviruses, can cross species boundaries more readily.

The Quest for COVID-19 in Wildlife

For spillover to happen, wild animals must encounter a high enough viral dose from humans. This most often occurs during direct contact with an infected person or through interactions involving pets and farm animals.

Indirect routes are also a concern; COVID-19 droplets could potentially contaminate wastewater, which could then expose wildlife, like marine mammals. For example, historic instances have shown that elephant seals in California fell ill with H1N1 during the 2009 swine flu outbreak—an event learned from the interplay between human activity and wildlife.

Current research efforts, such as our team’s study at Tufts, involve collaborating with veterinarians and wildlife rehabilitators to gather samples from various animals across the U.S. Nearly 300 specimens have been tested from a range of 20 species, including bats, seals, and coyotes, with no evidence of COVID-19 detected so far.

However, proactive monitoring is crucial. Similar to the case of the mink outbreak, surveillance in areas with infected captive animals can unveil risks in the wild.

The Implications: What If COVID-19 Takes Hold Among Animals?

The potential for viruses to adapt as they infect new species could have critical implications for human health. Adaptation, a process where viruses evolve to thrive in new hosts, can lead to unpredictable consequences. For example, since the emergence of SARS-CoV-2 in mink farms in Denmark, mutations have occurred that could affect vaccine efficacy, raising alarms among health experts.

Moreover, certain endangered species, like the black-footed ferret—closely related to minks—are particularly vulnerable to infection, heightening ecological concerns.

Historical precedent shows that spillover events can have dire consequences. In past decades, the Ebola virus devastated great ape populations after jumping from humans. Likewise, respiratory viruses have threatened the mountain gorilla's survival.

The greatest concern is that COVID-19 might establish a reservoir within new animal populations, posing a future risk of reintroducing the virus to humans. Research has confirmed that human-to-mink-to-human transmission has indeed occurred on Danish farms, marking a worrying cycle.

While our studies have yet to detect COVID-19 in U.S. wildlife, the alarm over infection in pets and zoo animals, coupled with the confirmed mink case, underscores a looming threat. Researchers urge continued surveillance and responsible practices to mitigate risks associated with this evolving situation.

Stay Informed: The Fight Against COVID-19 is Ongoing!

With new discoveries emerging daily, it’s crucial to stay updated and understand how our actions may impact wildlife and, ultimately, ourselves. The connection between human health and wildlife is more intertwined than ever—let’s protect both!