(CBS) — One of Chicago’s biggest medical centers says it’s never seen so many flu patients in one week.

Loyola Medicine says they set a new flu activity record last week at their clinics throughout the area.

READ MORE: Girl, 17, Among 2 Shot In Back Of The Yards

Doctors say people are getting sicker faster, CBS 2’s Roseanne Tellez reports.

“It hits fast, heavy and hard,” Dr. Jasmine Walton says. “Fevers, body aches, chills, a nagging cough. Typically, what the person tells me is, ‘I felt OK yesterday. I woke up today, and I feel miserable.’”

In doctors’ offices across the country, waiting areas are filled people suffering from symptoms of the flu.

Between Jan. 7 and Jan. 13, Loyola Medicine set a flu activity record with 190 confirmed cases.

READ MORE: Police Investigate Loop Carjacking

That was on the heels of a very busy December, when 357 cases were confirmed.

The total since the start of flu season: 730 diagnosed flu cases.

“This is the worst I’ve seen it,” Dr. Walton says.

If you want treatment, you must go to the doctors quickly, as soon as the first symptoms occur.

If you are still well, it’s not too late to get vaccinated.

MORE NEWS: Chicago Police Restrict Time Off For Officers; Unclear If Order Is Related To Battle Between City Hall, FOP Over COVID-19 Vaccine Mandate

More than 800 people have been hospitalized in Illinois, the state department of health says.