Local hospitals said they're seeing an unprecedented influx of flu patients.
Staff at St. Mary's Hospital have been busy treating what they say is a record number of flu cases.
"We see about a dozen a day that are coming in through the emergency room. Some of those (are) being admitted, some not, but right now in-house, we have at least two dozen patients, and a couple of those are children; most are middle-aged or older," said Ellen Smith, a nurse epidemiologist at St. Mary's Hospital.
The hospital has opened a contingency unit just for flu patients and has been stocking up on supplies to treat patients and protect staff.
"The more people that are not immunized, when we do have a virus that is easily spread like the one we're having this year, then we have a lot of people that are susceptible," Smith said.
Epidemiologists across the state said that two years of mild flu seasons have resulted in fewer people getting vaccinated this flu season.
The state Department of Health Services said this is the most severe season in five years and that cases are a month ahead of schedule.
Overloaded hospitals said that while they'll treat those who need it, people who are feeling ill are advised to stay home.
"Check with a health care provider, but certainly don't go in public and expose other people if you don't need to," Smith said.
In the Milwaukee area, emergency rooms at many hospitals are being inundated with older patients who have severe flu-like symptoms.
Over the past 10 days, many of those emergency departments have been forced to divert incoming ambulances to other hospitals.
A Milwaukee Health Department official said five to eight of Milwaukee County's 11 hospitals have reported rolling diversions -- temporary, periodic shutdowns of emergency departments except for life-threatening cases -- because staff and beds are strained by an influx of patients hit hard with the flu.
The state Department of Health Services is releasing new numbers on flu cases. As of Tuesday evening, more than 1,200 people in Wisconsin had to be hospitalized due to the flu.
There have been about 2,800 flu cases statewide, according to numbers updated last week. New numbers will be released Friday.