A few weeks ago, six different chains of infection were discovered by the delta variant B.1.617.2, with the additional mutation E48, in Uppsala County.
The falls were the first in Sweden and, among other things, several children at a school in Knivsta became ill.
But now that infection seems to have been pushed back.
- We do not know why, but we think it depends on several different factors.
One reason may be that there are many cold viruses in circulation and that people with those symptoms stay at home - and thus they do not infect more, says Mats Martinell at Region Uppsala.
It may also be that the new additional mutation is less contagious.
Hear Mats Martinell talk about more reasons in the clip above.