COVID mutates into new variants once or twice every 4 weeks.
Back during the summer we (here in the U.S.) had a variant that made COVID more transmissible.
COVID-19 Update: Coronavirus is Mutating and Becoming More Contagious; CDC Now Projects Up to 226,000 Deaths by mid-October; ; and More
https://www.docwirenews.com/docwire-pick/covid-19-update-coronavirus-is-mutating-and-becoming-more-contagious-cdc-now-projects-up-to-226000-deaths-by-mid-october-and-more/
D614G:
SARS-CoV-2, the virus behind the COVID-19 pandemic, is no exception. The coronaviruss RNA genome consists of about 30,000 base pairs. Since Chinese scientists first decoded the viruss genetic code in December, it has accumulated an average of one or two random mutations a month. One in particular, called D614G, may well have boosted diseases infectiousness.
https://www.uchealth.org/today/coronavirus-mutations-not-necessarily-cause-for-alarm/
D614G mutation promotes lysosomal trafficking of SARS-CoV-2 spike protein
https://www.news-medical.net/news/20201214/D614G-mutation-promotes-lysosomal-trafficking-of-SARS-CoV-2-spike-protein.aspx
Mutations making COVID-19 more contagious are, unfortunately, going to be an ongoing issue. As I wrote in another post, this new variant is likely all over the place. This morning cases were discovered in Netherlands. And I expect more.