You may have heard that bats are to blame for many disease outbreaks in recent years, including COVID-19 and SARS. But how exactly does a disease spread from bat to human? And with so many diseases coming from bats, you would think that bats would be sick all the time. It turns out this isn’t the case, and it’s likely because of the way that bats’ immune systems work.
Bats have very active immune systems to protect their cells from viruses. When a bat’s body detects a virus, a protein is released that sends a signal to the bat’s cells to keep the virus out. In response, viruses reproduce very quickly to try to get into the cells before this immune reaction triggers. Although the bats don’t get sick, these rapidly multiplying viruses can jump to animals with slower immune systems and can quickly cause serious infections.
At the same time, bats are great disease carriers. Bats live in large, crowded colonies—a perfect setting for viruses to spread. In addition, the average bat lives for around 30 years, which is a long time that an infected bat can spread the disease around its environment.