× Thanks for reading! Log in to continue. Enjoy more articles by logging in or creating a free account. No credit card required. Log in Sign up {{featured_button_text}}

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.