What Are Zoonotic Diseases? Causes, Symptoms, and Prevention

Medically reviewed by Dr. Baraa Alnahhal, MD · Last reviewed: October 2026

Quick Answer

Zoonotic diseases are infectious diseases that spread between vertebrate animals and humans, caused by bacteria, viruses, parasites, fungi and prions. They spread through animal contact, bites, insects, undercooked meat and contaminated food or water. Treatment depends on the germ. Handwashing, safe animal and food handling, preventing bug bites and recommended vaccines help prevent them. [1] [2]

What the research says

• Most human pathogens have animal origins: According to PubMed, a 2020 review found that more than 60% of human pathogens are zoonotic in origin, and that climate change, urbanization, animal trade, and travel have influenced how often and where zoonoses emerge. (Rahman et al., Microorganisms, 2020)

• Closely related hosts share more germs: In the largest manually compiled host-pathogen database to date, covering 2,595 bacteria and viruses and 2,656 vertebrate hosts, most pathogens were specialists that infect a single host species. The more closely related two host species were, the more pathogens they shared. (Shaw et al., Mol Ecol, 2020)

• Fast, complete rabies treatment matters: A systematic review of 52 articles (3,380 reviewed) identified 122 fatal breakthrough rabies infections in people who had started post-exposure treatment. In 56% (68 of 122), core steps such as wound cleaning or vaccine administration were not carried out correctly, and the authors conclude that breakthrough infection remains exceedingly rare when treatment is timely and appropriate. (Whitehouse et al., Lancet Infect Dis, 2023)

Key takeaways

Illness can pass between animals and people, which is why health is shared across species.

Understanding zoonotic diseases

Zoonotic diseases, also called zoonoses, are infections that originate in vertebrate animals, such as livestock, rodents, bats, birds, dogs, and cats, and can infect humans. Our bodies work in ways similar enough to other vertebrates that germs can sometimes adjust to live in both. [1] They are very common: scientists estimate that more than 6 in 10 known infectious diseases in people can spread from animals, and 3 in 4 new or emerging infectious diseases come from animals. [2] For a broader look at how infections spread, see our overview of infectious diseases.

How these diseases can change over time

• Animal-to-human only: some infections jump to a person but do not spread further from person to person.

• Human-to-human spread: diseases like Ebola can jump from animals to humans and then cause outbreaks by spreading between people.

• Mutation to human-only: some germs adapt so well to humans that they spread only among people, such as HIV and COVID-19. Once they spread only in humans, they are no longer considered zoonotic, although other forms of the germ can still exist in animals. [1]

Symptoms and causes

Because "zoonotic disease" covers many different infections, symptoms vary with the germ involved. Many systemic infections, however, share a common set of early signs. [1]

Common signs of infection

If you have been in contact with animals or have traveled to a high-risk area, watch for:

• General symptoms: fever, tiredness, and body aches.

• Head and breathing: headache or trouble breathing.

• Digestive symptoms: diarrhea and vomiting.

• Skin changes: rashes or unusual skin lesions. [1]

Early signs of zoonotic infections often look like the flu or a stomach bug.

Germs and examples

Zoonoses are grouped by the type of germ that causes them. [1]

• Bacterial: small organisms that often release toxins. Examples include Lyme disease, salmonella infection, anthrax, brucellosis, cat scratch disease, and plague.

• Viral: genetic material that hijacks human cells. Examples include rabies, bird flu (avian influenza), Ebola, and mpox.

• Parasitic: organisms such as worms or single-celled protozoa. Examples include toxoplasmosis, giardiasis, and cryptosporidiosis.

• Fungal: infections such as ringworm.

• Prion: abnormal proteins that damage the brain, such as variant Creutzfeldt-Jakob disease (vCJD), often called "mad cow disease."

How zoonotic diseases spread

• Direct contact: touching the saliva, blood, urine, mucus, feces, or other body fluids of an infected animal, including through bites and scratches. [2]

• Indirect contact: touching areas where animals live or objects they have contaminated, such as aquarium water, pet habitats, chicken coops, barns, soil, and pet food dishes. [2]

• Vector-borne: bites from ticks, mosquitoes, or fleas. [2]

• Foodborne: unpasteurized milk, undercooked meat or eggs, or produce contaminated with animal feces. [2]

• Waterborne: drinking or coming into contact with water contaminated by animal feces. [2]

Who is at higher risk

Anyone can get a zoonotic disease, but some people are more likely to be exposed or to become seriously ill. You may be at higher risk if you work with animals (for example on a farm or in a veterinary office), hunt or prepare wild animal meat, or have a weakened immune system. [1] Children under 5, adults over 65, and pregnant women are also more likely to get very sick. [2]

Diagnosis and management

Identifying a zoonotic disease takes careful evaluation, because many symptoms mimic common illnesses like the flu. Tell your provider about any animal contact, bites, or travel. [1]

Diagnostic procedures

1. Laboratory testing: samples of blood, stool, sputum (mucus coughed up from the lungs), or swabs from the nose or throat are checked for germs or antibodies. [1]

2. Imaging: when the lungs or other organs may be affected, a chest X-ray or CT scan can show damage. [1]

Treatment strategies

Treatment depends on the infection, and not every zoonotic disease has a specific medicine. [1]

• Antibiotics for most bacterial infections, especially if caught early.

• Antivirals for some zoonotic viruses.

• Antifungal creams or lotions for ringworm.

• Antiparasitic drugs for most parasitic infections.

• Monoclonal antibodies for some hard-to-treat diseases, such as Ebola.

• Surgery to remove cysts caused by some parasites.

• Vaccination and immune globulin after a possible rabies exposure. If an animal that may have rabies bites or scratches you, providers do not wait for symptoms: they clean the wound and give the vaccine and human rabies immune globulin to prevent infection. [1] Learn more in our guides to rabies and bat bites.

When to go to the emergency room

Go to the emergency room if you have signs of serious illness, including a high fever (over 103 °F / 39.4 °C), severe vomiting or diarrhea, confusion or other mental changes, unusual bleeding, a severe headache, or chest or abdominal pain. [1]

Outlook

Some zoonotic diseases can be very serious and even fatal. Viral hemorrhagic fevers such as Ebola and Marburg have a high death rate, and rabies is almost always fatal once symptoms start. Most other zoonotic illnesses are treatable and rarely fatal. [1]

Prevention and safety

Preventing zoonotic disease means reducing exposure and practicing consistent hygiene, especially if you work closely with animals or have a weakened immune system. [1][2]

Handwashing, vaccination, safe cooking, and bite protection lower your risk.

Personal hygiene and safety

• Handwashing: wash your hands with soap and clean running water right after being around animals, even if you did not touch them. If soap is not available, use a hand sanitizer with at least 60% alcohol, then wash as soon as you can. [2]

• Protective gear: wear gloves when handling animals, living or dead, and never handle wild animals with bare hands. [1]

• Avoid bites and scratches: see a healthcare provider if an animal that could have rabies, usually a bat in the United States, bites or scratches you. [1]

• Bug protection: wear long sleeves and long pants, use repellent with DEET, and check yourself and your pets for ticks. For more on mosquito-borne illness, see our guide to West Nile virus. [1]

Food and pet safety

• Food handling: cook meat to safe temperatures, wash your hands, surfaces, and utensils after preparing food, and avoid unpasteurized milk and foods made with it. [1]

• Water safety: do not drink or prepare food with untreated water.

• Veterinary care: keep pets healthy with regular check-ups, vaccines, and flea and tick prevention.

• Avoid bush meat: do not eat the meat of wild animals. [1]

• Vaccinations: if you are in a high-risk job or traveling to an area where a disease is common, ask about vaccines such as rabies. Many zoonotic illnesses do not have vaccines. [1]

Conclusion

Zoonotic diseases remind us how closely human health is tied to the animal world. Most infections are treatable and rarely fatal, but the possibility of serious illness and large outbreaks is real. Good hygiene, safe food handling, bite protection, and prompt medical care after an animal bite lower your risk. If you work with animals or have a weakened immune system, talk to your healthcare provider about a plan to stay safe. [1][2]

Frequently Asked Questions

What is a zoonotic disease?

An infectious disease that spreads between animals and humans.

What are other names for zoonotic diseases?

They are also called zoonoses.

What types of animals carry these diseases?

Almost any animal can, including bats, birds, cats, dogs, deer, livestock such as cows, pigs, and sheep, non-human primates, and rodents.

Can pets spread zoonotic diseases?

Yes. Cats and dogs can carry infections such as rabies, ringworm, and cat scratch disease.

How do zoonotic diseases spread?

Through contact with an infected animal's body fluids, bites and scratches, insect bites, undercooked meat, and contaminated water or food.

Can I get sick from touching an animal's urine or feces?

Yes. Contact with an infected animal's blood, urine, feces, or saliva is a common way to catch a zoonotic illness.

Is Ebola a zoonotic disease?

Yes. It starts in animals, spreads to people, and can then keep spreading from person to person.

Is COVID-19 still considered zoonotic?

It is thought to have started in animals, but it now spreads mainly from person to person. Once a germ spreads only among humans, it is no longer considered zoonotic.

What are common symptoms of a zoonosis?

Fever, tiredness, headache, body aches, rash, diarrhea, and vomiting.

Can zoonotic diseases cause a rash?

Yes. Many cause a rash or other skin changes.

Are all zoonotic diseases viral?

No. They can be caused by bacteria, viruses, parasites, fungi, or prions.

What are examples of bacterial zoonoses?

Lyme disease, salmonellosis, anthrax, brucellosis, plague, and cat scratch disease.

What are examples of parasitic zoonoses?

Toxoplasmosis, giardiasis, cryptosporidiosis, and trichinosis.

What is "mad cow disease"?

A prion disease officially known as variant Creutzfeldt-Jakob disease (vCJD).

How is ringworm spread?

It is a fungal infection that can pass to people through skin contact with an infected animal.

Who is at the highest risk?

People who work with animals or hunt, such as farmers and veterinarians, and people with weakened immune systems. Children under 5, adults over 65, and pregnant women are also more likely to become seriously ill.

Can children get zoonotic diseases?

Yes, especially through close contact with pets, farm animals, and animal exhibits. Children under 5 are at higher risk of serious illness.

Are zoonotic diseases fatal?

Some can be. Ebola and Marburg have high death rates, and rabies is almost always fatal once symptoms start. Most other zoonotic illnesses are treatable and rarely fatal.

Is rabies always fatal?

It is almost always fatal once symptoms appear, which is why treatment right after a bite is so important.

How do doctors test for zoonoses?

With samples of blood, stool, sputum (mucus coughed up from the lungs), or swabs from the nose or throat.

Can X-rays help diagnose these diseases?

Yes, chest X-rays or CT scans can show damage to the lungs or other organs.

Are there vaccines for zoonotic diseases?

Some, such as rabies, mpox, and Ebola vaccines. Many zoonotic illnesses do not have vaccines.

How are bacterial zoonoses treated?

Most bacterial infections can be treated with antibiotics, especially if caught early.

Do antivirals work for all zoonotic viruses?

No. Some viruses can be treated with antivirals, but others are managed with supportive care.

What are monoclonal antibodies?

Lab-made proteins that help the body fight an infection. They are used to treat some hard-to-treat diseases, such as Ebola.

Can surgery be part of treatment?

Yes. Some parasites form cysts that doctors remove with surgery.

How can I prevent bug bites?

Wear long sleeves and long pants, use repellent with DEET, and check yourself and your pets for ticks after being outside.

Is it safe to handle dead animals?

No. Wear gloves, never pick up a wild animal with bare hands, and wash your hands well afterward.

How should I cook meat to stay safe?

Cook it to the recommended safe internal temperature to kill germs.

Can contaminated water spread these diseases?

Yes, especially parasitic infections such as giardiasis.

Should I wash vegetables?

Yes. Wash fruits and vegetables well, and do not prepare food with untreated water.

How often should pets see a vet?

Regularly, so they stay up to date on vaccines and flea and tick prevention.

Can wildlife in my backyard be dangerous?

Yes. Rodents, birds, and other wildlife can carry germs, so avoid touching them and keep food and trash secured.

What is a vector?

An insect or other animal, such as a tick, flea, or mosquito, that carries a germ from one host to another.

Can mosquitoes spread zoonotic diseases?

Yes. West Nile virus, which circulates in birds and is spread to people by mosquitoes, is one example.

What is a prion?

An abnormal protein that damages the brain.

Can I get a zoonosis from a cat scratch?

Yes. Cat scratch disease is a bacterial infection that can follow a scratch or bite from an infected cat.

Is salmonella zoonotic?

Yes. It can spread from animals such as poultry and reptiles, or through food contaminated by animal feces.

Can birds spread flu to humans?

Yes. Avian influenza (bird flu) is a zoonotic virus.

What is toxoplasmosis?

A parasitic infection that people can catch from cat feces or undercooked meat. It can be dangerous during pregnancy.

Can I get sick from farm animals?

Yes. Livestock can carry germs such as those that cause brucellosis and salmonellosis.

Does hand sanitizer work?

It helps when soap and water are not available, if it contains at least 60% alcohol. Washing with soap and clean running water is better and removes more types of germs.

Can zoonotic diseases cause diarrhea?

Yes. Many bacterial and parasitic zoonoses cause diarrhea and vomiting.

Are zoonotic diseases a global problem?

Yes. Scientists estimate that more than 6 in 10 known infectious diseases in people can spread from animals, and 3 in 4 new or emerging infectious diseases come from animals.

What is the "One Health" approach?

A way of working that recognizes the connection between human, animal, and environmental health.

Can bats carry rabies?

Yes. In the United States, bats are the most common animal source of rabies exposure.

Can an animal look healthy and still spread germs?

Yes. Animals can appear healthy even when they carry germs that make people sick.

What should I do if a wild animal bites me?

Wash the wound well right away and get medical care, because you may need rabies treatment.

Where can I find more information?

The CDC's One Health pages and the World Health Organization offer reliable, plain-language information.

Related Reading

• What Is Rabies? A Plain-Language Guide to the Bite You Can't Ignore — and the shots that stop it.

• Bird Flu (Avian Influenza): Symptoms, Causes, and Treatment — a zoonotic virus carried by birds.

• Salmonella Infection Guide: Symptoms, Causes, Diagnosis, and Treatment — a common foodborne zoonosis.

• West Nile Virus: Symptoms, Transmission, and Prevention Strategies — a bird-and-mosquito virus that reaches people.

• Toxoplasmosis: What Causes It, Who Is at Risk, and How It Is Treated — a parasite linked to cats and undercooked meat.

References

1. Cleveland Clinic. Zoonotic Diseases. Cleveland Clinic. Last updated March 6, 2024. Accessed October 18, 2026. https://my.clevelandclinic.org/health/diseases/zoonotic-diseases

2. Centers for Disease Control and Prevention. About Zoonotic Diseases. CDC One Health. April 7, 2025. Accessed October 18, 2026. https://www.cdc.gov/one-health/about/about-zoonotic-diseases.html

3. Rahman MT, Sobur MA, Islam MS, et al. Zoonotic diseases: etiology, impact, and control. Microorganisms. 2020;8(9):1405. PMID 32932606. https://doi.org/10.3390/microorganisms8091405

4. Shaw LP, Wang AD, Dylus D, et al. The phylogenetic range of bacterial and viral pathogens of vertebrates. Mol Ecol. 2020;29(17):3361-3379. PMID 32390272. https://doi.org/10.1111/mec.15463

5. Whitehouse ER, Mandra A, Bonwitt J, et al. Human rabies despite post-exposure prophylaxis: a systematic review of fatal breakthrough infections after zoonotic exposures. Lancet Infect Dis. 2023;23(5):e167-e174. PMID 36535276. https://doi.org/10.1016/S1473-3099(22)00641-7

Medical disclaimer

This article is for informational purposes only and is not medical advice. Always consult a qualified healthcare professional for diagnosis and treatment decisions.