Why didn’t things like polio and smallpox mutate as much or as dangerously?
In: Biology
I do not have the exact answer, but I can provide quite a few generally valid reasons.
First, evolution is done by being randomly different from a previous generation. Then surviving long enough to have a new generation and pass it on. For animal, it’s pretty easy to understand, you live and reproduce, or your mutation dies with you.
For diseases though, it’s a bit more complicated. They don’t live alone. They NEED a host to live. Which mean they need quite a few condition to properly mutate.
1) Have a host survive long enough to have more generations. The more generations, the better (can be achieved by either not killing the host too fast, or reproducing fast. Or a combination of both)
2) Be able to transfer to a new host. It doesn’t matter if your new variant is super powerful and can wipe humanity, if nobody catches it before it dies, it’ll cause no harm.
Polio and smallpox were taken very seriously for centuries. Disease were things that could wipe out entire villages. But this made it difficult for these disease to fill the condition of mutating succesfully. Couple that with medicine, and it’s almost impossible.
Have an outbreak in a densely populated and developed area? Chances are you’re gonna get proper treatment, and isolation, preventing the disease from spreading.
Have an outbreak in a small village where they don’t have a doctor available? The village will die and nobody will have the disease anymore.
Covid is pretty much at the best situation: Careless people, lot of travel over large distance (so no shortage of hosts), fast reproduction, No early symptoms allowing it to hide long enough to get new host before the original even knows he’s infected. Our lifestyles have changed drastically over the last few decades, and they were no longer adapted to protect each others from disease.
Latest Answers