Featured Post from University of Florida

Batty pathogens: Why do bats spread so many diseases?

Oct 27, 2025

3 min

Jim Wellehan
CaptionResizeWrap TextRemove


Let’s face it — bats get a bad rap. Their links to disease outbreaks and their spooky association with vampires influence their notoriety. In reality, bats are truly remarkable. Bats support our agricultural industries as vital members of food webs. And, contrary to their portrayal in popular Halloween blockbusters, they are gentle and tidy creatures that groom themselves like cats.


So why is it that when we hear of disease outbreaks, it always seems to be bats?


According to University of Florida Emerging Pathogens Institute member Jim Wellehan, D.V.M., what sets bats apart isn’t black magic at all. But rather, it’s their long history of co-existing with viruses, the unique tradeoffs of flight and, perhaps most of all, a history of adapting to new pathogens.


“(Infectious disease) has been the biggest factor in all of evolution,” said Wellehan, who is also a professor at the UF College of Veterinary Medicine. “People are always looking for an excuse (as to) why bats are magic, and the truth is bats have just been exposed to a lot of stuff and selected for those genes accordingly.”


While humans are the most populous mammals on Earth, bats are a massive group of animals. Behind rodents, they represent the second-largest group of mammalian biodiversity, accounting for a whopping 20% of all mammal species. With over 1,400 species, it’s no surprise that pathogen diversity in bats is just as extensive and complex.


CaptionResizeWrap TextRemove




Jim Wellehan's research focuses on comparative infectious disease, pathogen evolution, molecular diagnostics and pathogen discovery.


View his profile here






Bats, as we know them, have been on Earth for over 50 million years. This extensive period has given pathogens plenty of time to evolve alongside the winged mammals. Bats carry viruses like Ebola, Hendra virus, Nipah virus and SARS-CoV-2, which causes COVID-19. One factor that is important in this viral diversity is flight.


Flight provides bats with many evolutionary advantages, such as predator evasion, access to new food sources and the ability to exploit diverse habitats. Flight also dramatically increases the chance of rapid pathogen transmission, as they can travel long distances and past many geographic barriers. Many species are highly social, which increases transmission rates as they live in close proximity and groom one another.




“When I first learned about Darwin and evolution, ‘survival of the fittest,’ I assumed, meant ‘smartest and fastest and strongest,’ but if you look at our genomes, turns out that's wrong,” said Wellehan. “The genes that are selected for are mostly immune-related. The most important thing is to have enough genetic diversity in your population so that someone has immunity genes that are effective against the next pathogen that doesn't even exist yet. With their increased mixing and contact rates, bats have done this more often than most animals.”


Generally, pathogens are most likely to cause disease when they first infect a new host species, as the susceptible animals have not yet developed the necessary defenses. Pathogens, along with their hosts, have no choice but to evolve to survive. With such a wide variety of species, it is not surprising that bats also carry a large proportion of mammal-associated viruses.


This is not to say that bats are immune to all pathogens. As the most rapidly evolving factor in life, infectious disease is an incredibly dynamic part of medicine. Bats can get sick from lyssaviruses, including rabies. Additionally, white nose disease, a fungal infection that targets hibernating bats, has been a growing concern in the United States for the past decade.


Though bat pathogens are a significant concern, habitat disturbance plays a larger role in bat population pathogen emergence, ultimately affecting humans as the dominoes fall.


“Pathogen transmission to humans and conservation efforts go hand in hand,” Wellehan said. “When populations get under stress, that's when ecological balances get shifted, and zoonotic jumps occur. ... It turns out that if we think of ourselves as something separate from nature, it doesn't work so well.”


So, while bats may embody the spirit of Halloween, their “magic” lies in evolution and resilience, shaped by millions of years of flying in the face of viruses, not spooky legends.

Looking to know more? We can help.


Jim Wellehan is available to speak with reporters about bats - simply click on his icon now to arrange an interview today.

Connect with:
Jim Wellehan

Jim Wellehan

Professor

Jim Wellehan's research focuses on comparative infectious disease, pathogen evolution, molecular diagnostics and pathogen discovery.

MycologyVirologyWildlife MedicineInfectious DiseaseBacteriology

You might also like...

Check out some other posts from University of Florida

2 min

Breakthrough with first disease-resistant wine grapes shows hope for a Florida wine renaissance

In a milestone for Florida agriculture, researchers have grown and harvested wine grapes that are resistant to the main bacterial disease that has long prevented the state from establishing a large-scale wine industry. Researchers successfully grew five grape varieties in Citra, Florida, that are resistant to Pierce’s disease, a bacterial infection that kills the vines and shrivels the grapes. The effort, led by Ali Sarkhosh, associate professor in the UF Institute of Food and Agricultural Sciences (UF/IFAS) horticultural sciences department, produced a harvest of grapes that resulted in 13 cases of wine. “This could be the start of a new chapter for Florida wine.” — Ali Sarkhosh, associate professor in the UF Institute of Food and Agricultural Sciences horticultural sciences department While Florida has a thriving muscadine grape industry, the global market for muscadine wine is small compared to wine made from Vitis vinifera, the species of grapes behind world-famous wines such as cabernet sauvignon, sauvignon blanc and merlot. Florida is already the nation’s second-highest wine-consuming state, behind only California, with an industry valued at $15 billion in 2022. Yet most of the wines served are produced elsewhere, primarily in California, Oregon and Washington. Sarkhosh said he hopes this research will offer a potential additional crop for muscadine grape farmers. As of 2017, there were 547 Florida vineyards, growing muscadine and hybrid grapes. “This could be an enormous opportunity for vineyards in Florida to expand into additional types of wine for a wider market,” he said. “This could be the start of a new chapter for Florida wine.” UF researchers worked with Château Le Coeur, a winery based in DeFuniak Springs, Florida, to make the wine from their harvest. The wine was crafted with 75% Florida-grown fruit and blended with 25% cabernet sauvignon and merlot. The grape used in the wine collaboration is a hybrid called “Erante Noir” and was developed at the University of California, Davis. It carries the genes of sauvignon blanc and cabernet sauvignon. John Choquer, the owner of Château Le Coeur, emphasized the potential for this collaboration. “If we are successful in growing in the area and combating Pierce’s disease effectively, it will be a strong growth industry and emerging market for agri-tourism,” he said. Early tastings point to a dark, fruit-forward wine. Château Le Coeur named this debut wine “Genial,” a French expression for something new and innovative. He said he is also planting a variety of traditional wine grapes, red and white, at his vineyard. He said his winery is grateful for UF’s support and collaboration as he works to create a Florida-based traditional wine industry. “This is not a short-term experiment,” Choquer added. “We plan to test more Pierce’s disease-resistant and traditional vinifera varieties, refine vineyard practices and build a new type of wine industry here in Florida. There will be challenges, there will be setbacks, but the potential is also so great. There is such a strong market potential here in Florida.”

2 min

Men experience greater eye changes from spaceflight, while brain differences between sexes are subtle

A new study into how spaceflight impacts the human brain and eyes revealed notable sex differences in brain fluid shifts, with female astronauts showing a greater reduction in fluid around the uppermost part of the brain than their male counterparts. Led by Rachael D. Seidler, Ph.D., director of the University of Florida’s Astraeus Space Institute and professor of applied physiology and kinesiology, the study analyzed data from astronauts to determine how factors such as sex, age and body metrics relate to structural brain and eye changes after space travel. The findings, published in August in npj Microgravity, provide key information for protecting astronaut health on long-duration missions to the moon and Mars. This is one of the first studies to look at sex differences in the physiological response to spaceflight. “The data on sex differences in response to spaceflight are scant, given the historically low number of female astronauts.” — Rachael D. Seidler, Ph.D., director of the University of Florida’s Astraeus Space Institute In addition to changes in fluid around the brain, the team also found that a form of eye compression, a hallmark of Spaceflight Associated Neuro-ocular Syndrome known as globe flattening, was the most consistent eye change among crew members. “By far the most prevalent sign of eye changes that we observed was globe flattening, suggesting that this should be the primary monitoring target for ocular health,” Seidler said. “Interestingly, eye changes were more prevalent in males than females.” Globe flattening, when the back of the eyeball becomes slightly indented or pushed inward, might sound minor, but it can have significant effects on vision and raise concerns for long-duration space missions. Surprisingly, there was no strong link between brain structural changes and eye changes, suggesting that the effects on the eyes and brain may arise from distinct mechanisms rather than shared physiological causes. The research underscores UF’s growing leadership in space health science. Through the Astraeus Space Institute, Seidler leads multidisciplinary collaborations that connect neuroscience, physiology and space research to advance human performance and safety in spaceflight. “We used UF's HiPerGator computing cluster for our analyses in this study, enabling us to analyze our data at high speeds,” Seidler said. Read the full study in npj Microgravity.

1 min

Mosquito-borne disease research featured ahead of climate conference

University of Florida medical geographer Sadie Ryan, Ph.D. is among the international scientists whose work is featured in the forthcoming “10 New Insights in Climate Science” report, which will be presented at the United Nations COP30 Climate Conference on Nov. 10. Ryan’s research, which examines how climate change influences the spread of mosquito-borne diseases such as dengue, contributed to a newly generated global map illustrating where shifting temperatures and rainfall patterns are making conditions increasingly suitable for disease transmission. “A lot of my research is about how vector-borne diseases are going to move as the climate changes, and what that means for where and when transmission can happen,” Ryan said. “Climate change isn’t the only driver of dengue’s spread, but we are seeing the bleeding edge of climate shifting those distributions, where it’s warm enough for long enough and wet enough at the right times for outbreaks to take off.” According to Ryan, the map included in the report is based on the most recent generation of climate models and directly illustrates how climate suitability for dengue is changing around the world. Produced annually by Future Earth, the Earth League and the World Climate Research Programme, the report synthesizes the most important developments in climate research at the intersection of climate, health and policy on the world stage.

View all posts
Powered by