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 bats also carry some pretty nasty pathogens. Some of the viruses they can carry are among the most deadly 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 because they live in densely populated colonies. Infections can spread from one bat to others, just like among people in a crowded subway or in a preschool classroom full of kids.

Bats also may be unaffected by diseases that can be fatal to humans. Researchers suspect that the extremes of bats’ body temperatures—from far below human body temperature when they’re in torpor (a hibernation-like state) to over 100 degrees when they’re in flight—make it difficult for viruses to reproduce in their bodies.

The behavior of some infected bats may result in more contact between bats and humans. For instance, bats infected with rabies may fly outside during the day. Bats can also migrate, spreading infection over long distances.

There is also concern that 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 can also live in cities, where there are in close proximity to humans.

Rabies

Most bats don’t have rabies—as of 2018 it has been found in about 6% of captured bats in the United States. Though most human cases worldwide are from dog bites, in the U.S. about 70% of cases are linked to bats.

Only a few human infections occur in the United States a year. Worldwide, however, rabies infects around 60,000 people a year. Almost everyone who has rabies dies—though a handful of people have survived.

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 scratched 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

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

Ebola and Marburg

After rabies, with a fatality close to 100%, Ebola and Marburg are two of the deadliest viruses that humans can get from animals. These viruses are believed to be primarily spread by bats.

A 2018 survey of bats in three African countries (Guinea, Cameroon, and the Democratic Republic of the Congo) found Ebola antigens in 18% of the tested bats. This means that those bats’ immune systems had previously encountered Ebola, though the researchers didn’t find any viral RNA in the bats.

Coronaviruses

Two other viruses that have had a real impact and have notably high mortality rates are SARS (Severe Acute Respiratory Syndrome) and MERS (Middle East Respiratory Syndrome). They are both are tied to bats.

SARS caused a multi-country, fast-moving, and deadly outbreak originating in China in 2002. The outbreak is thought to have been linked directly to bats.

MERS causes a severe and often fatal infection causing respiratory and renal failure. Known human cases were associated with camels, but it is thought to have originated in bats.

Bats are also considered to be a possible source of the SARS-CoV-2 virus that has caused the Covid-19 pandemic.

Nipah and Hendra Viruses

Nipah, a virus that has led to high human mortality in Asia, is also from bats. It spreads to people who drink date palm sap that has been contaminated by bats. It can also spread from pigs to humans and from humans to humans.

Hendra virus, which has caused fatal infections in humans and horses, is linked to bats in Australia. Only a few human infections have been identified, and are believed to have been transmitted from horses.

Histoplasmosis

In addition to all the viruses listed above, a potentially deadly 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.

A Word From Verywell

Bats 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. Even a bat that looks healthy might carry an unexpected disease.