Influenza (flu) is a seasonal disease that is most common in the winter and spring. Last year, almost 25,000 Marylanders sought care for flu symptoms. Anyone can get sick from the flu, but preschool age children (under 5 years of age), pregnant women and senior citizens are especially vulnerable to getting sick from influenza. People with chronic diseases (e.g. asthma or other lung conditions, heart problems, kidney disease, cancers and poor immune function) are at greatest risk for complications from influenza. Mild cases cause sudden onset of fever, cough, body aches, fatigue and other symptoms, which may last for up to two weeks. Severe cases can cause pneumonia, increase the severity of other chronic illnesses and lead to death. It is estimated that influenza kills 30,000 Americans annually.