Probing Evolution
Why Do Infections Kill? It’s Mostly Miscommunication
Killing the host means committing suicide, so why do it?
Pathogens, like any other lifeforms, have been selected by evolution for traits of successful reproduction or replication. There are 6 types of pathogens (or infectious agents): Bacteria, viruses, fungi, protozoa (tiny parasites), helminths (larger parasites like worms), and prions (infectious proteins).
But “for these tiny invaders, a dead host is a dead end,” Madeline Drexler, editor of Harvard Public Health magazine, wrote in the book, What You Need to Know About Infectious Disease. If pathogens meet the same fate as a dead host, why do they have the capacity to kill?
New Meeting Places
One reason is “new meeting places,” Drexler said. “Humans have cleared forests for agriculture and suburbanization, leading to closer contact with environments that may harbor novel (or newly introduced) pathogens.” International and wildlife trade, climate change, and traveling all contribute to “new meeting places” of pathogens as well.
Coronaviruses co-exist in bats but kill humans, for example. Coronaviruses have evolved to withstand the strong antiviral immunity of bats. Bats are the only mammal capable…
