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Zoonotic Diseases: How Animal Viruses Jump To Humans



While we don’t know exactly where the novel coronavirus came from, many scientists agree that it likely came from an animal. If that’s true, it means that COVID-19 is a Zoonosis, or Zoonosis– a disease caused by a pathogen that jumped from animals to humans.

The term Zoonosis They may not appear in regular conversations very often, but you certainly know some of them by name. Rabies, Lyme disease, AIDS, and the plague are known zoonoses, and scientists believe that Ebola virus disease and Severe Acute Respiratory Syndrome (SARS) also originate from animal viruses. But this list only scratches the surface.

A 201

7 study by researchers at the Centers for Disease Control and Prevention (CDC) estimated that 60 percent of the world’s known infectious diseases and up to 75 percent of new or emerging diseases are zoonotic, affecting approximately 2.5 billion people of one zoonotic disease are affected each year (although only 2.7 million of these cases result in death).

Types and overflows

But for any pathogen that manages to escape one host type and infect another (referred to as a) Spillover event) there are countless others who fail to make the leap. One reason for this is that different species don’t mix as closely as you might think.

“To the casual observer, it may appear that wildlife in native habitats are intermingled and in close contact with one another, but in fact each species is divided into a specific ecological niche based on their feeding strategies and environmental needs,” said Bruce Rideout, director for Disease Screenings at San Diego Zoo Global, Mental Floss says. “Each of these wildlife species will have a number of parasites or pathogens that have adapted to them, so these pathogens are typically restricted to the host’s ecological niche as well. As long as the ecosystems are intact, these pathogens stay in their home hosts and do not get into others. “

According to Rideout, the increase in spillover events over the past few decades is partly due to the fact that humans are more likely to disrupt wildlife ecosystems. But even if you wander through an undisturbed piece of forest and stroke all the animals you see, it is not a given that you will get sick.

For one, there is a possibility that the pathogens will not get into your body at all. Epidemiologist and veterinarian Julianne Meisner told Mental Floss that sometimes “the type of contact needed for transmission does not normally occur between an animal and a person”. It is possible that the animal only transmits a specific virus from mother to offspring, through sexual intercourse or through an insect that does not bite the human.

The perfect storm

But even if one of the animals did If a virus got into your body, it still needs to get into your cells. To do this, it binds to the receptors on the surface of the cell, which then envelop all or part of the virus. Once inside, the virus hijacks the cell’s systems and uses them to make more virus particles. However, if the virus cannot break through cell walls at all, it cannot survive – and luckily there are many animal pathogens specialized pathogensthat are only compatible with the cell receptors of this species. Generalistic pathogens, on the other hand, are much more diverse.

“The greatest threat to humans comes from generalist pathogens that are capable of infecting a wide variety of hosts, either because they use cell surface receptors that are conserved for a wide variety of species, or because they develop and evolve quickly Can adapt to a new host, ”says Rideout. For example, avian flu viruses can adapt to human infection after only one mutation.

How National Geographic There are reports of other factors that affect an animal virus’ ability to cause an outbreak in humans, including how long the virus can survive without a host, how well the virus can thwart a human immune system, and how often people come into contact with the virus come species that carry the virus. In many cases, a perfect storm never occurs and a virus does not evolve beyond its first human host.

Increased human interference in wild ecosystems, however, means more opportunities for generalist pathogens to jump to human hosts – and to predict which ones could cause the next outbreak or even a pandemic, scientists first need to locate undetected pathogens. Then they study their behavior to identify those capable of creating that perfect storm. While there are several organizations doing this type of research locally, nationally and internationally – for example, the PREDICT division of the US Agency for International Development for the Emerging Pandemic Threats program – the current pandemic has created a need for an intensified global one Cooperation underlined on this front.

It’s a small world

In a comment published in the July 2020 issue of scienceThe Wildlife Disease Surveillance Focus Group – a coalition of infectious disease experts, ecologists and other scientists from Washington University School of Medicine – advocated a decentralized, global database in which all research on animal pathogens can be stored and shared.

“In the past, prior to modern transportation, spillover events were local and slowly spreading, leaving people elsewhere free to respond,” said Jennifer A. Philips, co-director of the Infectious Diseases Division of Washington University and co-author of the article. said in a press release. “But now the world is so small that an event in one place endangers the whole world. This is not someone else’s problem. It’s everyone’s problem. “

Preventing the next zoonotic pandemic is not just about surveillance and research, but also about preserving wildlife ecosystems.

“It’s important for the general public to understand that the best way to protect human health is to protect the health of wildlife and ecosystems,” says Rideout. “The threat to us does not come from wildlife. It is about the destruction of the habitat and ecosystems of wild animals. We need to turn our attention to long-term sustainability. “




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