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COVID-19 is the latest example of zoonosis—here are 30 other diseases animals transmit to humans

  • COVID-19 is the latest example of zoonosis—here are 30 other diseases animals transmit to humans

    As COVID-19 spreads across the globe, the rapidly growing number of cases is alarming—largely because many are stymied by its origins. COVID-19 is an example of zoonosis: a disease or infection that is transmitted to humans from animals.

    COVID-19 is the name of the specific illness caused by the novel coronavirus. The exact origins of COVID-19 are not yet clearly understood, but the first outbreak of cases have been associated with a live animal market in Wuhan, China. It is thought that this particular coronavirus originated in bats who then infected the live animals sold in the market. The leap from animal to human was thought to have occurred because of humans’ close exposure to the animals in the market; but which exact animals were the source, and whether humans inhaled, ingested, or simply touched animal byproducts to become infected, is still unknown.

    Stacker used the Centers for Disease Control and Prevention (CDC) site and other public health resources to compile a list of 30 other diseases that are also transmitted by animals to humans. These illnesses range from diseases to infections and may cause a variety of symptoms, from vomiting and hallucinations to external rashes and sores. Though some are spread widely through the contamination of other surfaces by an animal’s bodily fluids, some can only be contracted through direct contact with a specific animal.

    Once humans are infected, they may be able to spread it from person to person—as is the case with Ebola, giardiasis, and ringworm—or it may only be contracted directly from animals—as with Lyme disease, Rocky Mountain spotted fever, and many other diseases. The ability for humans to transmit disease to one another after it is initially introduced from animals has historically been a dividing line between zoonosis cases that remain relatively uncommon, and those that have progressed into widespread national health concern—even pandemics like the one we are experiencing today.

    Read on to learn about some of the most notable animal-transmitted diseases, where they are found, and what can be done to treat them.

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  • Anthrax

    Those who inhale anthrax bacteria from infected animals can experience shortness of breath, sweats, extreme fatigue, and body aches. Exposure is so uncommon among the general public, however, that in the U.S. the anthrax vaccine is currently only made available to those who have an increased risk of exposure—such as veterinarians, farmers, livestock handlers, and laboratory workers.

  • Avian flu

    Wild aquatic birds and domestic poultry can spread this flu through their bodily fluids, including their saliva and feces. If a human accidentally inhales the virus, they may become infected, although this is uncommon. Typical avian flu symptoms include conjunctivitis, fever, pneumonia, and even seizures.

  • Brucellosis

    Cows, goats, and sheeps can pass on brucellosis bacteria into their milk. If that milk is left unpasteurized, humans who consume the ensuing dairy products can come down with fever, sweats, fatigue, and malaise. Some of those symptoms may never disappear.

  • Campylobacteriosis

    There are a variety of ways that humans can contract campylobacteriosis, including by eating undercooked or infected meat, seafood, produce, or other foods; by coming into contact with infected animals; or by drinking tainted water. Infected humans may experience fever, diarrhea, and stomach cramps, but will usually recover on their own after one week. The disease infects about 1.5 million people in the U.S. annually.


  • Cat-scratch disease

    True to its name, cat-scratch disease spreads to humans when infected cats lick, bite, or scratch a person and break their skin. Infected persons may develop infections around the scratch or bite area, as well as fever, reduced appetite, and fatigue. The disease can be prevented by washing scratches with soap and water immediately after they are inflicted.

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  • Cysticercosis

    Tapeworm eggs can develop in food, water, or surfaces that are contaminated with traces of fecal matter—which are then spread to humans when they unknowingly swallow the eggs via contaminated food or hand-to-mouth contact. Symptoms of cysticercosis depend on where the ensuing cysts develop: Cysts in the eyes often cause blurred vision, while cysts in the brain or spinal cord can cause seizure, headaches, and trouble with balance.

  • Dengue

    Similar to Zika and chikungunya, dengue is spread to humans through mosquito bites. Infected persons may experience fever coupled with nausea, vomiting, aching, or rash. These symptoms usually last up to a week, after which most infected persons will usually recover on their own—a welcome aspect of the virus, considering that there is currently no specific medication for the treatment of dengue.

  • Dog and cat flea tapeworm

    Because of the unusual way that dog and cat flea tapeworm is transmitted to humans, very few people become infected with the illness. Transmission occurs when humans accidentally swallow a flea that is carrying tapeworm larvae; accordingly, most who become infected are young children. Treatment is easily accomplished through the drug praziquantel, which dissolves the tapeworm internally.

  • E. coli infection

    E. coli is quite common across the U.S., with human infection most often occurring from eating undercooked beef or unpasteurized dairy. Animals that are able to pass E. coli to humans directly through their feces include cows, goats, sheep, and deer. Infected humans may experience diarrhea, fever, nausea, and vomiting.

  • Ebola

    Though Ebola is rare in the U.S.—cases are largely concentrated in sub-Saharan Africa—it is often deadly. The virus is transmitted through direct contact with an infected bat or primate. The U.S. Food and Drug Administration has approved the vaccine rVSV-ZEBOV (“Ervebo”), which protects against the Zaire ebolavirus species of Ebola.

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