Influenza

Influenza is an acute respiratory illness caused by infection with influenza type A or B virus. It typically occurs in outbreaks over a five-to six-week period each winter. Each year, hundreds of thousands of excess hospitalizations, tens of thousands of excess deaths, and billions of dollars in health care costs can be attributed to influenza and its complications. Attack rates can Nurse Jacqueline Spaky delivers an swine flu injection to an elderly patient in New York City in 1976. The city set up 45 sites at which to give the shots free of charge in an attempt to limit the spread of the deadly disease. Older adults are more susceptible to catching the flu, and its affects can often be much more harsh than in younger patients. (Corbis/BETTMAN photo.) be as high as 10 to 40 percent in the community, and examination of influenza epidemic curves typically reveals a bimodal pattern, with attack rates highest in the young and morbidity and mortality highest in the elderly population. In most studies, elderly persons with chronic respiratory conditions account for up to 80 percent of patients with such serious complications as hospitalization and death.

Influenza can be a particularly difficult problem for people who live in long-term care facilities (LTCFs), where case fatality rates during outbreaks often exceed 5 percent. Up to 22 percent of residents that acquire influenza will develop complications of infection severe enough to result in hospitalization. Once influenza is introduced into a LTCF by staff and visitors, these relatively closed communities are an ideal setting for the rapid spread of influenza by droplet transmission. Attack rates among residents can exceed 40 percent.