Scientists have found SARS-CoV-2 spreads like a virus among white-tailed deer and other wild animals in the United States.
People are the likely source, but that doesn’t mean the virus can’t evolve among these animals and then spill back into humans, and researchers are worried about what this spread means for the risk of future pandemics.
There’s little doubt SARS-Cov-2, the virus that caused the ongoing pandemic, came from an animal — almost certainly a bat. And the prevailing scientific opinion is that there as an intermediate host, an animal of some sort, that was infected by a bat or bats and then infected people.
It’s also clear that people can infect animals. Pets such as cats, zoo animals such as gorillas and snow leopards and farmed mink can all be infected. Multiple cases have been reported, and evidence of changes in the viruses infecting mink have led to mass culls of those animals on fur farms.
The latest species to capture the attention of wildlife biologists are white-tailed deer. It’s little surprise that farmed deer would catch the virus from people. Any visitor to a deer farm knows the animals behave like goats, shoving their wet noses into the pockets, hands and faces of human visitors or caregivers as they clamor for food and treats — and setting themselves up for infection.
But how are wild deer catching it?
Viral spread among deer
“If somebody might bite an apple and throw it or even if I sneeze in a tissue and drop it,” speculated Dr. Suresh Kuchipudi of the Animal Diagnostic Laboratory at Pennsylvania State University, who helped lead one study published earlier this month that found 80 percent of deer they tested across Iowa between November of 2020 and January of 2021 showed evidence of infection.
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Scientists have found SARS-CoV-2 spreads like, a virus among white-tailed deer and other wild animals in the United States.
Sewage has been found to carry the virus, so polluted water might be a source, he added, or people spitting or contaminating the environment in other ways. The deer may then spread the virus to one another.
“Keep in mind these are highly susceptible animals and while you do not know how much virus they need to be infected,” Kuchipudi told CNN. “It raises the urgent question — we know the deer are effectively transmitting virus among themselves, and then who are they giving it to?”
It’s also possible another species could be picking up the virus from people and infecting deer.
“We don’t know what’s going on in our very own country and we need to find out,” said Hon Ip of the United States Geological Survey in Wisconsin.
Viral hotspots among the rodents
Ip and colleagues tested animals they found around a mink farm that was the site of an outbreak in Utah and found skunks, mice and other animals were susceptible to a variety of coronaviruses.
They were originally worried that the mink, which caught the virus that causes Covid-19 from people, might infect the local wildlife. They found no indication of that. “It was a very pleasant surprise,” Ip told CNN.
But the mice, raccoons, skunks and other animals carried a load of other coronaviruses. “The number of coronaviruses and the diversity was a surprise,” Ip said.
“Our findings indicate an unexpectedly high prevalence of coronavirus among the domestic and wild animals tested on mink farms and raise the possibility that these operations could be potential hot spots for future trans-species viral spillover and the emergence of new pandemic coronaviruses,” they wrote in a report published in the journal Viruses in October.
Researchers like Ip and Kuchipudi say much more study like this is needed.
Kuchipudi and colleagues conducted their study after the US Department of Agriculture published research in July that found 40% of deer tested in four states had antibodies to the SARS-CoV-2 — evidence they’d been infected.
There are several reasons scientists do not want to see a virus like the one that causes Covid-19 infecting animals. For one, it creates what’s known as a reservoir — so that even in the unlikely case that everyone got vaccinated and the virus stopped circulating among people, it would still circulate among animals and could re-infect people eventually.
More likely however, is the risk that it could change and evolve. That can happen in two ways.
One is steady adaptation. As it infects different species, the virus will change to better adapt to those species and that could make it either more or less dangerous to humans.
Another route to change: viruses can take shortcuts by swapping big chunks of genetic material in a process called recombination. Influenza is especially good at this, but coronaviruses can do it, as well. If an animal is infected with more than one coronavirus at a time, the two types can mix and match genes and potentially come up with new variants.
“Recombination is one of the major mechanisms for coronavirus evolution,” Ip said. So if animals are already carrying their own varieties of coronavirus, and people are then infecting them with strains that cause pandemics among humans — the potential exists for these viruses to infect animals at the same time, trade genetic material, and give rise to new pandemic viral species.
“This raises very urgent questions about the trajectory of this pandemic,” Kuchipudi said.
If there are animals out there like white-tailed deer that are so easily infected and that so easily transmit the virus among themselves, that’s a red flag.
That means much better surveillance is needed to see what other animals might be getting infected by people or by other animals, and what threat they might pose to other animals and to people.
“We need to be prepared for any variants that might emerge,” he said.
Plus, Ip said, surveillance is needed to know what coronaviruses are living in animals that might be the source of the next pandemic — not just among bats in remote caves in southeast Asia, but perhaps among mice or deer or raccoons in the backyards of the US Midwest.
And people need to remember that humans are the primary source of the spread of the virus. Even if Covid-19 originally came from animals, humans are the species that have amplified and spread it.
And there’s one answer to that spread. “Vaccination rates are not uniform across the world,” Kuchipudi said. “As long as there are susceptible human beings, we give opportunities for the virus to circulate and change. There need to be more concerted efforts to vaccinate as many people as possible so that we can at least minimize transmission among human beings.”
Prior to early 2020, the average person never uttered the word ‘coronavirus’ and had no reason to think they would soon be part of a global effort to practice social distancing. As the COVID-19 surged, these terms, and others, became commonplace in news reports and daily conversations.
Stacker consulted encyclopedias and public health websites to compile a list of 25 virology terms. These terms help build background knowledge on what viruses are, how contagious they are, how they work in living cells, how they spread, and how they affect humans. These definitions illustrate the difference between the common cold and the COVID-19 virus and why COVID-19 is so deadly. The terms also help show why self-isolation and quarantine—as well as social distancing—are critical, as these practices help “flatten the curve” and prevent an exponential rise in COVID-19 cases and deaths. This story will also highlight terms such as capsid, R0, and zoonosis that are increasingly used in news stories.
Keep reading for fast lessons in droplet spread, community transmission, quarantine, and many more COVID-19-related terms.
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A virus is a microscopic, infectious cellular invader. Viruses insert themselves into living cells where they replicate. They can infect most life forms: from bacteria to plants to animals. Every cellular organism studied so far has its own viruses. Millions of viruses are found across all ecosystems and life forms on Earth, with about 5,000 of these described by science.
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A bacteriophage—or phage for short—is a virus that specializes in infecting bacteria. Most viruses are bacteriophages. These particular types of viruses are made of proteins that infect the bacterial cell, then they enclose the DNA or RNA genome within the cell. Bacteriophages are the most common entities on Earth and are found everywhere bacteria exist, which is across all environments on Earth.
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Viruses specialize on all different forms of cellular life; each virus evolved to infect different forms. Animal viruses infect only animals, and two fields of study separate their study. For non-human animals, the field is known as “veterinary virology,” while “medical virology” is the study of viruses and human beings. Viruses that affect humans are the most studied with many areas of research.
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The protein shell of a virus that helps it enter its target cell is called a capsid. It protects the gene material of the virus. Structures of capsids vary widely and may consist of numerous proteins.
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Some capsids build what are called “viral envelopes” from the cell itself. These are lipid membranes the virus builds around itself, with lipid material of the cell’s inner membrane. Viral envelopes are thought to help the virus infect the target cell. Lipids are the cell’s fatty acids and are not water soluble.
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Endocytosis is the term for when a virus enters its target cell. Viruses infect their cells in various ways. In some cases, the virus enters the cell but leaves the capsid behind, on the outside of the cell. In enveloped viruses, the viral envelope fuses directly with the cell membrane then it enters the cell. Inside the cell, the capsid degrades and the genetic material of the virus is released.
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Some viruses have a special trait that allows them to enter and infect a cell, then go dormant. The virus may replicate in the cell at first, then stop. Viral latency refers to the time that viral genetic material can remain in the cell before being reactivated. If reactivated, the virus can reinfect the host without the host being re-exposed. HIV is known to have viral latency.
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Zoonosis is when an infectious disease is transmitted from other vertebrate animals to humans. These kinds of infections can occur in natural conditions because vertebrate animals are genetically similar to humans. Some examples include the black plague, transmitted by rats; rabies, transmitted by bats, raccoons, and dogs; and anthrax, transmitted by sheep. More recently emergent human diseases like HIV, Ebola, and SARS likely arose from zoonosis.
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Infectious particles like viruses can travel on dust or simply be suspended in the air. These particles can settle onto various surfaces, then can stir up and re-suspend in the air. If an uninfected person is exposed to these infectious particles, that person can become infected via airborne transmission. Some people have caught measles by entering a room where people with measles had recently been.
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Community transmission occurs when an infectious disease arises in a community in which there is no connection to a known case, and/or no known history of travel into or out of a region with the disease.
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The “basic reproduction number” is also known as R0 (“R-nought”), a measure that describes how easily a virus spreads. Specifically, R0 is an estimate of how many other people get infected by one infected person. For example, seasonal flu has an R0 of about 1.3 while COVID-19 estimates suggest 1.5 or more people can be infected by each carrier, with some research indicating an R0 factor being as high as 6.68. Changes to R0 can happen with how often people see others, location, and strength of the efforts to lower spread.
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An epidemic is defined by Merriam Webster’s dictionary as “an outbreak of disease that spreads quickly and affects many individuals at the same time.” An epidemic is a situation in which a disease is actively spreading.
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A pandemic results from an epidemic that has grown past geographic boundaries. It is a type of epidemic. It occurs over a wide geographic area and impacts “an exceptionally high proportion of the population”—likely a whole country or the entire world. On March 11, 2020, the World Health Organization categorized the new coronavirus (COVID-19) as a pandemic.
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Antiviral drugs are medications that are used to inhibit viruses and their development. Antibiotics typically destroy the infectious agent, but since viruses are not exactly alive, antiviral drugs are designed to interfere in some way with the virus.
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Vaccines prevent disease. A vaccine contains the same germ that makes people sick, but it is rendered harmless: Either it’s killed or weakened to the point it does not cause illness. When the vaccine is injected into the body, the immune system responds by making antibodies, leading to the same immunity a person would have if they’d become sick and recovered. When enough people are immune, this protects whole populations because of the diminished chances of an outbreak.
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The common cold is a viral infection of the nose and throat that causes various symptoms like sore throat, runny nose, headaches, cough, and low fever. Many viruses can lead to the common cold, and most healthy people recover from a cold in six to 10 days.
The term coronavirus defines a “family of viruses that cause illness ranging from the common cold to more severe diseases, such as Middle East Respiratory Syndrome (MERS-CoV) and Severe Acute Respiratory Syndrome (SARS-CoV). The novel coronavirus [most] recently discovered has been named SARS-CoV-2 and it causes COVID-19.” Coronaviruses are not the flu.
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The novel coronavirus that causes the disease COVID-19 is known as SARS-CoV-2. Although this new disease may have certain similar symptoms to seasonal flu, It is from a completely different family of virus, and its particular set of traits make it highly contagious and far deadlier. The Centers for Disease Control has an information sheet to help people decide if they might have the new coronavirus, and what to do if they are sick.
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Isolation separates those who have a disease from those who don’t, or who are not known to be sick. The public has been guided on isolating at home during the pandemic if they or their family members have symptoms. The CDC fact sheet also provides guidance on home isolation and what to do once you no longer have symptoms.
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Social distancing is when people stay away from each other, avoid all crowds, and cancel large and small events and gatherings. Social distancing effectively keeps this virus from spreading between people, and thus saves lives—particularly in the current pandemic because of its extreme contagion and high fatality rate. Distancing has included closing schools, working remotely, staying at least 6 feet apart from other people, and connecting with loved ones using online platforms, phones, and social media.
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If people have been exposed to someone with the contagious disease, quarantine separates and restricts their movement to see if they get sick. Quarantine helps ensure that if someone is already exposed, that they stay away from others. People can shed the infectious virus and infect others without knowing they’re contagious.
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“Flattening the curve” is a key way to save many, many lives by slowing the exponential spread of the disease. This allows time for health-care workers, hospitals, and related systems to help infected people, without becoming overwhelmed by exponentially rising numbers of seriously ill patients. It is very effective, may last from weeks to months, and could save tens of thousands of lives.
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