Epidemics, which are often transmitted by common pests like rats and mosquitoes, pose a much bigger threat than most people realize. Genetic mutations are happening all the time, in almost every species. They’re happening in large animals like us, and they’re happening in bacteria, viruses, and protozoa—and in these little guys, they happen much faster.
Most mutations happen in non-coding regions of DNA, and are thus irrelevant. Coding-region mutations (the ones that matter) are usually bad for the species: DNA codes for RNA which codes for proteins, and if coding DNA is mutated, it usually results in messed-up proteins downstream.
But every once in awhile, a rare coding-region mutation leads to a species being much better off in its environment—and that “environment” can be the African savannah, a hot-spring, or a mammalian host (like us!).
All of evolution is driven by mutations. Mutations introduce an element of random chance that leads different members of a species to express slightly different genes. Natural selection favors certain genes over others, and weeds out the organisms that aren’t well adapted to their environment. But environments change, often dramatically (e.g., the Ice Age). Changing environments lead to natural selection favoring different genes—and thus to evolution. And humans are causing rapid, profound environmental changes.
Infectious agents and their hosts are fighting a constant evolutionary arms race—hosts develop resistance to infectious agents, and infectious agents develop resistance to host defenses (such as our immune systems, antibacterial drugs, and antiviral drugs).
A certain agent that infects humans, be it a bacterium or virus, could undergo the right mutation(s) at the right time—and it could be deadly for us. These organisms wouldn’t “want” to kill us, because most of them require a living host to spread themselves to other hosts. But infectious agents have killed us in huge numbers before.
With the way the world is connected in the 21st century, if a traveler in a major airport were infected with something new and extremely virulent, the entire world could be infected virtually overnight. And although we probably have the medical technology to eventually thwart any such disease, it could take months before the right medication or vaccine were developed and deployed—enough time for millions (or more) to die.
Because pests can start epidemics, do your part to save humanity and call us with any pest problem so we can deal with it and you can rest easy.
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