- A zoonotic disease is an illness that can be passed from an animal to a human.
- Some examples of zoonotic diseases include rabies, salmonella, Lyme disease, malaria, and COVID-19.
- These diseases are passed through direct contact with an animal, contact with infected droppings or other bodily fluids, through a vector such as a mosquito or a flea, or by eating infected, uncooked meat.
- This article was medically reviewed by Tania Elliott, MD, who specializes in infectious diseases related to allergies and immunology for internal medicine at NYU Langone Health.
- Visit Insider's homepage for more stories.
A zoonotic disease is any disease that can be passed between animals and people. Some examples of zoonotic diseases are ebola, swine flu, and the COVID-19 coronavirus.
Zoonotic diseases are common, ranging from mild symptoms to potentially deadly illnesses. Experts estimate that over 60 percent of infectious diseases can be spread from animals to humans.
Here's what you need to know about zoonotic diseases and how to protect yourself from getting them.
How zoonotic diseases go from animals to people
Many different types of germs can cause a zoonotic disease including bacteria, viruses, parasites, and fungi. "There are several ways that zoonotic pathogens move from animals to people," says Richard Ostfeld, PhD, a disease ecologist at the Cary Institute of Ecosystem Studies. These pathways include:
- Direct contact with an animal like from a scratch or bite. Common examples include being bitten by a dog with rabies or getting cat scratch fever.
- Contact with the urine, feces, or nests of an infected animal. This can happen when cleaning out a shed where animals may have nested or when swimming in contaminated water. This contact can happen in one of two ways:
- Vectors such as mosquitos, ticks, and fleas can spread disease by biting an infected animal and then biting you.
- Food transmission can result from eating food contaminated with animal feces or from eating undercooked animal products like meat or eggs.
Examples of common zoonotic diseases
Rabies: One well-known zoonotic disease is rabies, a deadly condition that is transferred through an animal bite. Rabies has traditionally been associated with dogs. In fact, dogs are the source of 99 percent of rabies cases, mainly in Africa and Asia.
In the US, rabies is rare. Moreover, dogs are vaccinated against rabies, so the most common sources are wild animals like bats and raccoons. Once a person starts showing symptoms like agitation and confusion, the disease is almost always fatal.
Lyme Disease: Lyme disease is the most common zoonotic disease in the US. Symptoms include rash, fatigue, headache, and fever. The disease is transmitted through the bite of a blacklegged tick. Mice are typically the carriers of Lyme disease, and when a tick bites an infected mouse, it then carries the disease to any human it bites.
If Lyme disease is not treated, it can spread through the whole body, affecting the heart and nervous system. Even if you do get treatment, you may still have long-term symptoms of pain and fatigue.
Salmonella: Salmonella is a bacterial infection that affects 1.35 million people in the US every year. Salmonella is generally spread through infected chicken or eggs, but it can come from a variety of foods including other meats and vegetables.
The symptoms of Salmonella, including fever, diarrhea, and cramps, are unpleasant, but most people recover without antibiotics in 4 to 7 days.
Malaria: Malaria is a parasitic illness caused by a bite from an infected mosquito. In 2018, there were 228 million cases of malaria worldwide, mostly in sub-Saharan Africa and South Asia. Malaria causes flu-like symptoms including chills, aches, and nausea. If left untreated, it can be fatal.
How to prevent and treat zoonotic diseases
"There are relatively few vaccines for zoonotic diseases," Ostfeld says, but this is becoming a bigger focus for scientists after outbreaks of zoonotic viruses like Ebola and COVID-19. One challenge to developing a vaccine may be that some zoonotic diseases mutate into many different forms, making it difficult to create a universal vaccine.
Zoonotic diseases are treated depending on the type of germ they come from. Bacteria are treated with antibiotics, while parasites can be treated with anti-parasitic drugs, Ostfeld says.
"Handling, killing, and eating wildlife is definitely risky," Ostfeld says. Being in rodent-infested buildings can also increase your risk, as rodents are the source of many zoonotic infections, Ostfeld says.
One important step to protect yourself against zoonotic disease is to use insect repellents or protective clothing to keep away ticks and mosquitoes.
It's also important to always wash your hands after touching or being around animals. If you can't wash your hands right away, you can use a hand sanitizer with at least 60 percent alcohol to kill germs.
Zoonotic diseases are a common cause of illness and it's important to take precautions whenever you may come into contact with animals. If you start to feel ill after having contact with an animal or animal droppings, go see a doctor as soon as possible.
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