Flu is a respiratory virus that circulates each year, typically in the colder months, infecting a large number of people from all age groups, and making them ill. High-risk individuals for flu infection include those living with diabetes, asthma, and heart disease, older adults above 65, infants under 6 months, those with weakened immunity, and or those living in nursing care facilities. Some of the common symptoms of influenza or flu include high fever, chills, sore throat, cough, body aches, and fatigue. Possible complications of flu include pneumonia, bronchitis, sinus, and ear infection.
There are four types of influenza viruses, viz. A, B, C, and D. A and B types cause seasonal epidemics while C type causes mild respiratory illness. D type primarily affects cattle. About 5 to 20 percent of the US population (10 million to 50 million) get flu infection each year.
The Flu shot can save you from infection and save lives. However, the flu virus changes (mutates) each year, and its different versions or strains infect people each year. So, even if you had a shot last year, you should take a flu shot this year also as you might not have the protection against the new strain of flu virus circulating this year.