The Delta variant of SARS-CoV-2, the virus that causes COVID-19, is quickly spreading across the world. The World Health Organization estimates it will be the dominant strain globally within months, reports MarketWatch. In the United States, Delta already is—and that’s a big problem, especially for the unvaccinated.

Full doses of the vaccines seem to offer robust protection against Delta despite it being more transmissible than previous variants. This is one of the reasons U.S. officials have now warned the pandemic has shifted to become a “pandemic among the unvaccinated.”

So where is Delta’s spread potentially the most hazardous in the United States? Where vaccination rates are low.

Read the full article about Delta variant danger zones by Michael Grothaus at Fast Company.