Preliminary data from hospitals across the city indicates that more patients went to emergency rooms complaining of flulike symptoms — such as fever and a cough — in the week ending Dec. 20 than during any other week in the past decade.

New York City’s syndromic surveillance system, which collects information about every patient who visits an emergency room, reported 9,857 visits for “influenza-like illness” last week. That was higher than in the worst weeks of the 2017-18 or 2024-25 flu seasons, both ranked as “high severity” by the Centers for Disease Control and Prevention.

Laboratory tests for the flu — which include people who went to a doctor’s office, along with those who went to the emergency room — underscored the vast reach of the virus. Last week, New York City recorded 32,239 laboratory-reported cases of flu — more than half of those cases were children. That surpassed the worst week of the 2024-25 flu season, when there were 23,308 laboratory-reported cases.

The picture is much the same across the state.

“We are seeing the highest number of flu cases ever recorded in a single week in New York State,” State Health Commissioner Dr. James McDonald said, noting that the state recorded 71,123 flu cases for the week ending Dec. 20. That was the most recorded in a single week since 2004, when the state began its current method of reporting cases.