MINNEAPOLIS (AP) — Minnesota health officials are warning that the highly contagious delta variant of the coronavirus now accounts for more than 75% of the state’s new COVID-19 cases.

And they say it’s a serious threat to unvaccinated people as the state’s case numbers head back up. Kris Ehresmann, the state’s infectious disease director, says the delta variant has gone from causing less than 1% of Minnesota cases to over three-quarters in just a few weeks.

Health Commissioner Jan Malcolm made a plea for Minnesotans who haven’t been vaccinated to get their shots. She says breakthrough cases” among vaccinated Minnesotans remain “very rare.”