Influenza—the fancy word for the flu—is an infectious respiratory disease, caused by a virus, that can be really dangerous to at-risk groups, including the older people, infants and people with chronic diseases. Flu and bacterial pneumonia—a common complication of flu—each year send 200,000 people to hospitals in the United States and cause on average 36,000 deaths.
Immunizations usually help individuals avoid the flu, but public health officials are concerned that this season, people may be reluctant to be inoculated. That’s because last year’s circulating virus strains did not match up with the vaccine, so more people came down with the flu.
Vaccine formulations are determined each year by scientists who look at the dominant strains in the Southern Hemisphere. In February they recommend the three viruses that are most likely to strike the United States in the next flu season. Usually one or two strains are used from the previous year’s vaccine. But this year’s formulation is “unprecedented,” says Anthony S. Fauci, M.D., director of the National Institute of Allergy and Infectious Diseases (NIAID), because the vaccine has been manufactured with three new strains.