Wisconsin and much of the U.S. is experiencing a "second wave" of late-season flu cases, the state health department said Monday.
An increasing number of those cases also involve a strain of the influenza virus that this season's vaccine is ineffective against, the Wisconsin Department of Health Services said. Vaccine effectiveness is expected to continue to decrease.
And the flu season in Wisconsin has yet to peak, with high numbers of cases expected well into April, according to the health department.
A Centers for Disease Control and Prevention map of flu cases nationwide shows that the virus was widespread throughout most of the U.S. through March 16.
In Wisconsin, most of the state was experiencing high rates of flu-like illness activity through March 16, according to a map from the state health department. The southeastern part of the state, not including Dane County, was the only region of Wisconsin "below baseline" through the same date.
The state said the flu led to 390 people being hospitalized in the week ending March 16.
The flu has killed one person in Wisconsin between Oct. 1, 2018 and March 16, according to the health department.
Symptoms of the virus -- which is spread by infected people or by objects they've touched -- include chills, fever, headaches, body aches, sore throat, tiredness, dry cough and a runny or congested nose, according to the health department.
Though most with the virus recover within two weeks, it is especially dangerous to those over 65 years old, are pregnant or have a medical condition like diabetes or kidney disease.
In addition to vaccination, frequent hand washing, avoiding contact with infected people, and disinfecting surfaces that are touched often are ways to avoid contracting the flu.
Those infected should stay home from work or school and avoid going out for at least 24 hours after a fever disappears without the use of medication.