What's so bad about bats?

bats. getty

Well, bats actually 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.

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.

It is also questioned whether deforestation leads to some bats having more contact with people. This may especially be 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.


Most bats don't have rabies, but some - often times 5-10% - do. Most human cases are from dog bites, but bats are the principle reservoir for rabies (as well as its origin).

Few people are infected.

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).

Prophylaxis is important for preventing infection. It is not just those who have touched a bat who need to have prophylaxis for rabies. Who needs prophylaxis:

  • Anyone bitten by a bat
  • Any potential bat saliva exposure to mouth, wound, nose, or eyes
  • If a person awakes and find a bat in the room
  • If a bat is found in a room with an unattended child
  • If a bat is found in a room with someone without the cognition to recognize a bat bite

Everyone should wash with soap and water any bites or other areas of exposure.

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%.


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 Hendraviruses

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. It's the disease featured in the movie Contagion because of what it can do.

Hendravirus 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.


It's not just viruses. A fungus found in the soil can also be found in bat droppings, guano. It can lead to pulmonary problems as well as blood problems especially in people with immune system problems.

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. This has happened with Rabies, but can happen also with all of these other infections.

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