Influenza, also known as the flu, is a contagious respiratory disease caused by different strains of viruses. In the United States, there is a flu season that begins every fall and ends every spring. The type of flu people get during this season is called seasonal flu. Flu viruses spread from person to person when people who are infected cough or sneeze. Adults may be able to infect others 1 day before getting symptoms and as long as 5 days after getting sick.

The following groups of people are at an increased risk: people age 50 or older, pregnant women, people with chronic medical conditions, children age 6 months and older and people who live with or care for anyone at high risk.

People at high risk should have their vaccinations updated every year and receive pneumococcal pneumonia vaccine if age 50 or older, as directed by their physician.