Covid-19 has mutated to be more infectious
but not more severe

https://medicalxpress.com/news/2020-07-infectious-strain-covid-dominates-global.html

Sample quote

"Data provided by our team in Sheffield suggested that the new strain was associated with higher viral loads in the upper respiratory tract of patients with COVID-19, meaning the virus's ability to infect people could be increased.

"Fortunately at this stage, it does not seem that viruses with D614G cause more severe disease."

End quote