Influenza (the flu) is a contagious respiratory illness caused by a virus. There are many types of flu viruses, including type A and B, that circulate throughout the world each year.  Symptoms of flu can be mild to severe, and at times can lead to death. In the United States, about 5% to 20% of the population become infected with the flu virus annually. Of people who get the flu, more than 200,000 are hospitalized, and about 36,000 die from complications caused by the flu each year.

Connecticut residents are also affected by the flu. Each year, the Department of Public Health (DPH) receives between 2,000 and 3,600 laboratory confirmed reports, representing up to approximately 1% of the state population. The actual number of flu cases each year may be up to five times higher, since most people do not seek medical attention or testing when they are ill. 

The DPH Epidemiology and Emerging Infections Program maintains influenza surveillance by tracking the results of reported flu tests. Flu updates are prepared on a weekly basis using the surveillance data. These weekly updates will be posted on the DPH Flu Statistics page throughout the influenza season, which runs from October through May. This update provides information on the cirulating flu types and a breakdown of the cases by sex, age group, and county of residence. 

Summaries of additional indicators of flu activity are also provided in these weekly updates. These summaries include information from a network of physicians who report on patients with flu-like symptoms. Information is also provided from two surveillance systems that report on seriously ill cases that are seen in emergency departments or admitted into Connecticut hospitals.

CDC National Weekly Flu Activity Map