Biting midges have been in Iceland for a long time. This article from 2000 (in Icelandic) mentions 4 species of biting midges, 1 of which preys on mammals, including humans.

In 2015, a new species of biting midges appeared and started spreading through South and West, and that species turned out to be much more aggressive, and also much smaller than the native species, meaning it can get through the bug nets over the windows and bite people in their sleep.

Reports of excessive midge bites became much more prevalent following this new species, which is why that "problem" dates to that year, although biting midges are not new.