Researchers in Beijing and Shanghai found the more aggressive strain appeared to have evolved from the other but has become less common since early January, with the older version returning.
Source: TWO strains of the killer coronavirus are spreading, study claims
senior1938voice comment to readers:
This is a long, very informative read, answers questions that were asked earlier on, a bit repetitious at the beginning, but read on down the article, lots of worthwhile facts…
Viruses Dead End Here & Much More 