Over the course of the COVID-19 pandemic, researchers have found coronavirus infections in pet cats and dogs and in multiple zoo animals, including big cats and gorillas. These infections have even happened when staff were using personal protective equipment.

More disturbing, in December the United States Department of Agriculture confirmed the first case of a wild animal infected with SARS-CoV-2, the virus that causes COVID-19. Researchers found an infected wild mink in Utah near a mink farm with its own COVID-19 outbreak.

Are humans transmitting this virus to wildlife? If so, what would this mean for wild animals – and people too?

How viruses hop between species

We are two scientists who study viruses in wildlife and are currently running a study investigating the potential for SARS-CoV-2 transmission from humans into domestic and wild animals.

When viruses move from one species into another, scientists call it spillover. Thankfully, spillover doesn’t occur easily.

To infect a new species, a virus must be able to bind to a protein on a cell and enter the cell while dodging an immune system the virus hasn’t encountered before. Then, as a virus works to avoid antibodies and other antiviral attackers, it must replicate at a high enough volume to be transmitted on to the next animal.

This usually means that the more closely related two species are, the more likely they are to share viruses. Chimpanzees, the species most closely related to humans, can catch and get sick from many human viruses. Earlier this month, veterinarians at the San Diego Zoo announced that the zoo’s troop of gorillas was infected with SARS–CoV–2. This indicated it is possible for this virus to jump from humans to our close relatives.

Some viruses tend to stay in a single species or in closely related species, while other viruses seem innately more capable of large species jumps. Influenza, for example, can infect a wide variety of animals, from sparrows to whales. Similarly, coronaviruses are known to regularly jump between species.

The question of how many and which species can be infected by SARS-CoV-2 – and which ones might be able to support continued circulation of the virus – is an important one.

Searching for COVID-19 in wildlife

For human-to-wildlife spillover of SARS-CoV-2 to occur, an animal needs to be exposed to a high-enough viral dose to become infected.

The highest-risk situations are during direct contact with humans, such as a veterinarian’s caring for an injured animal. Contact between a sick person and a pet or farm animal also poses a risk, as the domestic animal could act as an intermediate host, eventually passing the virus to a wild animal.

Another way COVID-19 could spill over from humans into animals is through indirect infection, such as through wastewater. COVID-19 and other pathogens can be detected in waste streams, many of which end up dumped, untreated, into environments where wildlife like marine mammals may be exposed. This is thought to be how elephant seals in California became infected with H1N1 influenza during the swine flu pandemic in 2009.

To study whether spillover of SARS-CoV-2 is happening, our team at Tufts is partnering with veterinarians and licensed wildlife rehabilitators across the U.S. to collect samples from and test animals in their care. Through the project, we have tested nearly 300 wild animals from over 20 species. So far, none – from bats to seals to coyotes – have shown any evidence of COVID-19 by swab or antibody tests.

Other researchers have launched targeted surveillance of wild animals in places where captive animals have been infected. The first confirmed infection in a wild mink was found during surveillance near an infected mink farm. It’s not yet clear how this wild mink got the coronavirus, but the high density of infected minks and potentially infectious particles from them made it a high-risk location.

Bad for animals, bad for humans

When a virus infects a new species, it sometimes mutates, adapting to infect, replicate and transmit more efficiently in a new animal. This is called host adaptation. When a virus jumps to a new host and begins adapting, the results can be unpredictable.

In late 2020, when SARS-CoV-2 jumped into farmed mink in Denmark, it acquired mutations that were uncommon in humans. Some of these mutations occurred in the part of the virus that most vaccines are designed to recognize. And it didn’t just happen once – these mutations independently arose in mink farms multiple times. While it’s not yet clear what impact, if any, these mutations may have on human disease or the vaccine, these are signs of host adaptation that could allow novel variants of the virus to persist and reemerge from animal hosts in the future.

Another risk is that SARS-CoV-2 could cause disease in animals. Ecologists are especially concerned about endangered species like the black-footed ferret, which is closely related to minks and thought to be very susceptible to the virus.

Human-to-wildlife spillover has happened before. In the late 20th century, the Ebola virus jumped from humans into great apes and has resulted in devastating consequences for these endangered animals. More recently, a human respiratory virus has been detected in threatened mountain gorilla populations and has caused deaths as well.

But perhaps the biggest risk to humans is that spillover could result in the coronavirus establishing a reservoir in new animals and regions. This could provide opportunities for reintroduction of COVID-19 into humans in the future. This month researchers published a paper showing that this had already happened on a small scale with human–to–mink–to–human transmission on mink farms in Denmark.

While our team has found no evidence of COVID-19 in wild animals in the U.S. at this time, we have seen convincing evidence of regular spillover into dogs and cats and some zoo animals. The discovery of the infected wild mink confirmed our fears. Seeing the first wild animal with natural COVID-19 is alarming, but sadly, not surprising.

Jonathan Runstadler, Professor of Infectious Disease and Global Health, Cummings School of Veterinary Medicine, Tufts University and Kaitlin Sawatzki, Postdoctoral Infectious Disease Researcher, Tufts University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

I nervously fell into a long line of fellow first graders in the gymnasium of St. Louis’ Hamilton Elementary School in the spring of 1955. We were waiting for our first injection of the new polio vaccine.

The National Foundation for Infantile Paralysis – with money raised through its annual March of Dimes campaign – had sponsored field tests for a vaccine developed by Jonas Salk. The not-for-profit had acquired sufficient doses to inoculate all the nation’s first and second graders through simultaneous rollouts administered at their elementary schools. The goal was to give 30 million shots over three months.

Now, more than six decades later, attention focuses on the rollout of two COVID-19 vaccines, following their emergency use authorization by the U.S. Food and Drug Administration. States have begun to administer them in a rocky and frustratingly slow delivery process – while hundreds of thousands of new cases continue to be diagnosed daily in the U.S.

While not necessarily comforting, it is useful to recognize that the early days and weeks of mass distribution of a new medication, particularly one that is intended to address a fearful epidemic, are bound to be frustrating. Only after examining the complex polio vaccine distribution process as documented in papers collected in the Dwight D. Eisenhower Presidential Library did I come to understand how partial my childhood memories actually were.

Vaccine distribution, 65 years ago

After I received my polio shot, I remember my parents’ relief.

The polio virus causes flu-like symptoms in most people who catch it. But in a minority of those infected, the brain and spinal cord are affected; polio can cause paralysis and even death. With the distribution of Salk’s vaccine, the much-feared stalker of children and young adults had seemingly been tamed. Within days, however, the initial mass inoculation program went off the rails.

Immediately following the government’s licensing of the Salk vaccine, the National Foundation for Infantile Paralysis contracted with private drug companies for US$9 million worth of vaccine (around $87 million today) – about 90% of the stock. They planned to provide it free to the country’s first and second graders. But just two weeks after the first doses were administered, the Public Health Service reported that six inoculated children had come down with polio.

As the number of such incidents grew, it became clear that some of the shots were causing the disease they were meant to prevent. A single lab had inadvertently released adulterated doses.

After considerable fumbling and outright denial, Surgeon General Leonard Steele first pulled all tainted vaccine off the market. Then, less than a month after the initial inoculations, the U.S. shut down distribution entirely. It wasn’t until the introduction of a new polio vaccine in 1960, created by Albert Sabin, that public trust returned.

History’s lessons for 2021

This story offers several lessons relevant to the COVID-19 vaccine distribution just now getting rolling.

First, federal coordination of an emergent lifesaving medical product is critical.

The federal government had declined to play an active oversight and coordination role for the polio vaccine, but still wanted the credit. The federal Department of Health, Education and Welfare (now Health and Human Services) offered no plan for distribution beyond the privately funded school-based program.

The department waited a full month after the vaccine was first administered before bringing together a permanent scientific clearance panel. That delay had less to do with formal procedures than with the ideological opposition of Health, Education and Welfare Secretary Oveta Culp Hobby.

Hobby was a political appointee who had taken office just months before the vaccine was approved. Her reluctance to involve the federal government in matters that she believed were best left in private hands – and her oft-stated fear of “socialized medicine” – meant that safety checks would be left to the private labs producing the vaccine. The results immediately caused dire problems and even avoidable deaths.

Second, the polio vaccine distribution process demonstrated how vital it is for the federal government to act in ways deserving of public trust.

In those hopeful first few weeks of the polio vaccine distribution, those of us lining up for shots had little to fear beyond the sting of an injection. That changed quickly.

Once some children had in fact been harmed by the shot, obfuscation by government officials, clumsy explanations and delayed responses engulfed the entire production and distribution process in confusion and suspicion. Trust in the government and the vaccine eroded accordingly. Gallup polls found that by June 1955, almost half of the parents who responded said they would not take any further vaccine shots – and the full regimen of polio inoculation required three doses. In 1958, some drug companies halted production, citing “public apathy.” It wasn’t surprising to see a startling upsurge in polio in 1959, doubling cases from the previous year.

Today, with COVID-19 already highly politicized – polls suggest that a minority of Americans will decline to take any vaccine – it is critical to administer an effective vaccine delivery program in a manner that builds trust rather than undermines it.

Scattered reports of allergic reactions to the COVID-19 vaccine have generated not the denials of the Eisenhower administration but rather honest and realistic responses from the Centers for Disease Control and Prevention. Particularly for vaccines that require multiple inoculations – both Pfizer and Moderna vaccines require two shots administered with a 21- or 28-day gap – mass inoculations will require not just an initial willingness to get the first dose but the maintenance of trust sufficient to get people back for the followup.

There are significant differences in the social-political contexts of the era in which the polio vaccine was distributed and today, including the nature and threat of the two diseases and the technologies of the vaccines. But time and again, the COVID-19 pandemic has revealed disconcerting parallels with mistakes made in the past. The good news is vaccination works – no case of polio has originated in the U.S. since 1979.

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Bert Spector, Associate Professor of International Business and Strategy at the D'Amore-McKim School of Business, Northeastern University

This article is republished from The Conversation under a Creative Commons license. Read the original article.