What are flu-related deaths?
Flu-related deaths are deaths that occur in people for whom influenza infection was likely a contributor to the cause of death, but not necessarily the primary cause of death.
Does CDC know the exact number of people who die from flu each year?
CDC does not know exactly how many people die from flu each year. There are several reasons for this: First, states are not required to report individual flu cases or deaths of people older than 18 years of age to CDC. Second, influenza is infrequently listed on death certificates of people who die from flu-related complications [12]. Third, many flu-related deaths occur one or two weeks after a personâs initial infection, either because the person may develop a secondary bacterial co-infection (such as a staph infection) [1,8,11] or because influenza can aggravate an existing chronic illness (such as congestive heart failure or chronic obstructive pulmonary disease) [3]. Also, most people who die from flu-related complications are not tested for flu, or they seek medical care later in their illness when influenza can no longer be detected from respiratory samples. Influenza tests are only likely to detect influenza if performed within a week after onset of illness. For these reasons, many flu-related deaths may not be recorded on death certificates. These are some of the reasons that CDC and other public health agencies in the United States and other countries use statistical models to estimate the annual number of flu-related deaths. (Flu deaths in children were made a nationally notifiable condition in 2004, and since then, states have been required to report flu-related child deaths in the United States through the Influenza Associated Pediatric Mortality Surveillance System).