Flu is very infectious and can be passed easily from person to person.
Moreover, people infected with the flu are contagious usually 2 days before their own symptoms of fevers, coughs and aches begin. The flu can be debilitating even for healthy people, and is particularly serious for the elderly or patients with chronic medical conditions. One way to minimize your risk of getting the flu is through immunization. The protection provided by a flu vaccination takes about 2 weeks to develop and lasts approximately a year. However since the flu viruses change each year, immunization is needed every year.