Zoonotic diseases are infectious illnesses that spread between animals and humans. Bacteria, parasites, viruses, fungi and prions can cause them. Zoonotic diseases spread through contact with infected body fluids, animal bites, contaminated water and eating infected meat. Bats, livestock, rodents, birds and other vertebrates can carry them.
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Zoonotic diseases, or zoonoses, are infectious diseases that can spread between animals (vertebrates) and humans. Vertebrates are animals with a backbone, like cows, sheep, rats, dogs, cats, bats and birds. The way their bodies work is similar enough to ours that pathogens (germs) can sometimes adjust to live in both.
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Some zoonotic diseases only spread from animals to humans and don’t spread from person to person. Others, like Ebola, spread from animals to humans and continue to spread in humans, causing periodic outbreaks of illness. Still others spread to humans and then mutate to only infect humans, like HIV and COVID-19. Once they only spread in humans, they’re no longer considered zoonotic (but other forms of the disease can still exist in animals).
Symptoms of zoonotic diseases vary depending on the specific illness. Some common symptoms include:
Many different pathogens can cause zoonoses. These include:
Many pathogens only infect one specific type of organism — humans, specific animals, plants or even other germs. But zoonotic diseases have the ability to infect both humans and other vertebrates. Or at one time, they infected only specific animals, but mutations allowed them to “jump” to humans and cause an infection.
Most zoonotic illnesses are bacterial, parasitic or viral. Other zoonoses include ringworm (a fungal infection) and variant Creutzfeldt-Jakob disease (vCJD, commonly called “mad cow disease”), a form of prion disease.
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Bacteria are small, single-celled organisms that often release toxins that can make you sick. Examples of bacterial zoonoses include:
Parasites can be parasitic worms, protozoa (single-celled organisms) or ectoparasites, like lice and mites. Examples of parasitic zoonoses include:
Viruses are small pieces of genetic information in a container that use our cells to make more copies of themselves. Examples of viral zoonoses include:
Zoonotic illness can spread through:
Almost any animal can carry zoonotic illnesses. Examples include:
You might be at higher risk for zoonotic infections if you:
Healthcare providers usually diagnose zoonotic diseases with a sample of tissue or body fluid, including:
Depending on your symptoms, you may also need imaging tests, like a chest X-ray or CT scan.
Treatment for zoonotic illness depends on the infection. Not all zoonotic diseases have specific medications that get rid of the infection. Treatment might include:
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Ways you can reduce your risk of infection with a zoonotic disease include:
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Yes, some zoonotic diseases can be very serious and even fatal. Viral hemorrhagic fevers (like Ebola virus and Marburg virus) have a high mortality (death) rate. Rabies is always fatal once symptoms start. Most other zoonotic illnesses are treatable and are rarely fatal.
Talk to your healthcare provider if you work with animals or are at higher risk for zoonoses. They can help you reduce your risk and know what symptoms to look out for.
Go to the emergency room if you have signs of serious illness, including:
Whether they’re beloved companions at home, pets or farm animals that you keep healthy at work, or wildlife that you appreciate from afar, the connection between humans and animals can be profound. But that connection can mean that some bacteria, viruses and other germs can spread illness between humans and animals.
Fortunately, there are many precautions you can take to keep both yourself and your animal friends safe and healthy. Most serious zoonotic illnesses are rare. If you’re at higher risk for zoonotic diseases — because of your work, hobbies or a compromised immune system — talk to your provider about your concerns. They can help you come up with a plan to reduce your risk, recognize symptoms to look out for and get treatment quickly if you need to.
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Last reviewed on 03/06/2024.
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