Humans seem to have introduced SARS-CoV-2, the virus causing COVID-19, in mink populations, pet dogs and cats, wild deer, captive gorillas, and an assortment of other species.

Quantum Magazine reported that the transmission of an infection from humans to animals is colloquially referred to as a  "spillback" of organisms. Such infections could have major effects on wild species and humans.

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When scientists are thinking about the movement of bacteria between animal species, there's a focus on "spillover" occurrences in general, when pathogens are moving from animals to humans. However, transmission is not a one-way street.

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Diseases Shared Between Humans and Animals
(Photo: Nathan Stirk/Getty Images)
A survey conducted in 2014 showed that humans were found to have the ability to transmit ‘over 20 bacterial, 12 viral, and seven fungal pathogens to animals’ and that wild animals are the most affected, followed by pets and livestock.


Diseases Humans can Transfer to Animals.

In 2020, a report from The Wire Science specified that it's frequently forgotten that humans transmit diseases to animals. In a survey conducted in 2014 worldwide, humans were discovered to have the ability to transmit "over 20 bacterial, 12 viral, and seven fungal pathogens to animals." the results also showed that wild animals are the most affected, followed by pets and livestock.

For instance, the hepatitis A virus induces hepatitis in non-human primates. On the other hand, herpes viruses may infect marmosets and tamarins.

Meanwhile, Salmonella bacteria could cause infection in pet and farm animals, while the mumps virus is known to infect dogs.

Essentially, infectious disease spillover between humans and animals is a two-way street. However, a number of scientists focus on the transmission of the disease from humans to animals, a phenomenon known as "reverse zoonosis or anthropozoonosis."

An example of zoonosis is the possible transfer of COVID-19 from humans to cats, both domestic and wild.

Spillback Effects on Human Health

When infectious bacteria repeatedly reproduce in different animal species, their evolutionary trajectory may differ among species, possibly creating novel strains that could escape immunity if reintroduced to humans.

For instance, the case of Staphylococcus aureus, a microbe that can cause diseases that range from minor skin infections to pneumonia and drug-resistant staph infections.

S. aureus has a wide range of hosts, prospering in mammals from dolphins to mountain goats and in many species of birds and fish.

As with armadillos, multiple studies have used genomic sequencing to restructure species jumping from humans to animals, then back to humans.

Zoonotic Diseases

According to the Centers for Disease Control and Prevention, zoonotic diseases are caused by hazardous germs such as parasites, fungi, viruses, and bacteria.

Such germs can result in various illnesses in animals and people, ranging from mild to severe diseases and even death.

According to zoonotic disease, animals can appear healthy even when they are carriers of germs that can turn people ill.

These conditions in animals are very typical in both the United States and worldwide. Scientists approximate that more than six out of 10 known infectious diseases in people can be transmitted from animals, and three out of every four new infectious diseases in people from animals.

The health agency is working 24 hours a day, seven days a week, to protect humans from zoonotic diseases in the US and worldwide.

Due to the close link between humans and animals, it is essential to be aware of the common ways people can get infected with bacteria that can cause zoonotic diseases.

Related information about animals and humans sharing diseases is shown on the CDC's YouTube video below:

 

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