American scientists have found a new strain of the coronavirus – and it looks to be more contagious than the early versions.
As well as being more contagious, it means that people who have already had Covid-19 could get infected again.
Wherever the new strain appeared, it quickly infected far more people than the earlier versions from Wuhan.
Scientists working on vaccines told The Los Angeles Times that they are hoping the virus does not constantly change like flu virus does. This would mean a new vaccine every year.