Despite its widespread reputation for being mild, the ultratransmissible omicron coronavirus variant is sending a record number of people to emergency departments and hospital rooms in the US, swamping health care systems nationwide.

As of January 15, omicron’s highest seven-day average of daily cases was nearly 799,000—a 386 percent increase from the highest average of daily cases seen during the delta wave (from July to the end of October). Similarly, omicron’s highest daily average of emergency department visits was 86 percent higher than that of delta’s, and hospital admissions were 76 percent higher.

The latest data comes from a study published by the Centers for Disease Control and Prevention on Tuesday. The study highlights that, even though the omicron wave has been marked by relatively smaller proportions of severe cases and deaths, the variant’s extraordinary spread has still overwhelmed hospitals and extracted a devastating toll.