Originally Posted by
bluejuice71
Due to warmer weather or some other factor? Seems to be exploding in Brazil which is hot.
Viral attenuation is a thing. As a virus moves through a population, it weakens through a process called lethal mutagenesis. Basically mutations build up reducing the efficacy and eventually wind up killing off the virus.
They also make vaccines from this process by forcing attenuation. These vaccines are called “live attenuated”.