Diseases That Can Be Spread by Bats

Bats help us. They play an important role in our ecosystem. They eat insects that are agricultural pests, pollinate and spread seeds, and fertilize plants with their waste (guano).

But they also carry some pretty nasty pathogens. Some of these infections are among the most deadly there are to humans: Ebola, SARS, Rabies, MERS, Marburg, Hendra, and Nipah. Thing is, the bats don't mind. They are a bit like the honey badgers of the viral world. They often do not get sick from infections that could be deadly to us.

Mexican Freetail bats in flight at dusk, Tadarida brasiliensis. Carlsbad Caverns National Park. New Mexico. USA
John Cancalosi / Getty Images

Why Bats?

Diseases may spread from bat to bat easily. They live in tight colonies. Infections can bounce between one bat to another, just like among people in a crowded subway or in a preschool classroom full of kids.

Bats also may be seemingly unaffected by a disease that can be fatal to humans. Bats have a colder body temperature and can tolerate viruses humans cannot. The behavior, though, of some bats when infected with diseases may result in more contact of bats with humans. For instance, bats can behave strangely when they have rabies, such as flying outside during the day. Bats can also migrate, spreading infection far away.

There is also some debate over whether deforestation leads to some bats having more contact with people. This may especially be true when forests are fragmented, becoming islands of trees and ecosystems, with people living in the swaths of lands surrounding these forest islands. Bats also, as they fly, can bring diseases from one area to another; they often live in urban areas as well.

Rabies

Most bats don't have rabies, but it's believed that up to 5% to 10% of sick or captured bats may. Most human cases are from dog bites, but bats are the principal reservoir for rabies (as well as its origin).

Few people are infected. The US sees 2-3 infections a year; worldwide 160 die a day, 60,000 a year. Almost everyone who has rabies dies—though 5 have lived (among the 36 who have received a new, experimental protocol).

The best way to avoid getting rabies is to avoid exposure to wild animals, and for some professions and exposures, there is a rabies vaccine. For people who have close exposure or bites, prophylaxis is important for preventing infection. It is not just those who have touched a bat who need to be vaccinated. Here is a list of people who should get the vaccine:

  • Anyone bit by a bat
  • Any potential exposure to bat saliva via your mouth, nose, eyes, or an open wound
  • Anyone who wakes up and finds a bat in the room
  • Children who may have been exposed to a bat in their room

If you notice a bat bite, wash the area thoroughly and go to the ER immediately. Call your doctor and public health office as well. If the bat is dead, try to keep it for further testing.

Ebola and Marburg

After rabies, whose fatality has been close to 100%, Ebola and Marburg are two of the most deadly per case infections. These viruses also spread from bats.

Studies have found Ebola in 5% of adult bats in affected areas (Gabon and Republic of the Congo) during outbreaks (and none in young bats). Levels were lower in between outbreaks—and interestingly even higher in pregnant bats: 33%.

Coronaviruses

Two other viruses that have had a real impact and have notably high mortality rates are MERS and SARS. They are both are tied to bats. SARS caused a multi-country, fast-moving and deadly outbreak originating in China 2002-3. Its outbreak has been thought to be linked directly to bats. MERS causes a severe and often fatal infection causing respiratory and renal failure and has been spreading in hospitals in the Middle East. It is connected to camels—but it also thought that bats played a role.

Nipah and Hendra Viruses

Nipah, a virus that leads to high mortality in people in Bangladesh and Malaysia, is also from bats. It spreads from bats to people through date palm sap which is drunk by bats and then later by people. It has also spread among pig farms in Malaysia.

Hendra virus, which has caused fatal infections in humans and horses, is tied to bats in Australia. Close to 50% of the bat species involved were positive.

Histoplasmosis

In addition to all the viruses listed above, a special fungus can be spread by bats and their droppings. Histoplasmosis is an infection that typically involves the lungs but, especially in people with immune system problems, can infect virtually all organs including lymph nodes, bone marrow, and brain.

Bats though are an important part of our ecosystem. Without them, other diseases can flourish, such as those spread by the bugs that they eat. However, they haven't controlled mosquitoes (and mosquito-borne diseases) as much as hoped; they just don't eat enough mosquitoes.

It's important not to touch bats you don't know are safe. They can look healthy but carry a disease we didn't expect.

Was this page helpful?