The Flu Symptoms 2025. A weekly influenza surveillance report prepared by the influenza division. Influenza (flu) is a contagious disease with mostly respiratory symptoms caused by infection with an influenza virus.
However, if you develop symptoms of the flu and are at higher risk for serious complications from the flu—or if you become very sick or concerned about your. Flu vaccines are updated for each winter to give protection against the strains of flu that are most likely to be going around.