Compared with flu A, flu B is relatively stable and doesn't change as much from year to year, so many adults have immunity to it from infections earlier in life.
The Wisconsin Department of Health Services says 11 people have died of flu complications this season.
This season so far has been particularly deadly for children, with 27 deaths reported through December 28.
The latest increase in flu cases comes after State Health Commissioner Dr. Howard Zucker this past December declared influenza prevalent in New York State.
According to health officials, "in CT, the Department of Public Health uses multiple systems to monitor circulating influenza viruses".
There are regular flu shots that are approved for use in people 65 years and older and there also are two vaccines designed specifically for people 65 years and older. Annual summaries are also posted for comparison. The Flu Tracker is a dashboard on the New York State Health Connector that provides timely information about local, regional and statewide influenza activity.
For more information on influenza and vaccination, visit the Center for Disease Control and Prevention (CDC) website. The organization estimates that flu has resulted in between 9.2 million and 35.6 million illnesses each year in the United States and several deaths.
"It's not too late to get vaccinated", according to the CDC.
It's impossible to accurately predict where the flu season is heading, but if it continues on its current trajectory, this year will be one of the worst ever.
According to the CDC, the flu infects the respiratory tract.