The influenza virus is a contagious virus that primarily affects the respiratory system, causing symptoms like fever, cough, and body aches. It spreads easily through droplets when an infected person coughs or sneezes. There are several strains of the virus, including influenza A, influenza B, and influenza C, with influenza A being the most common and often responsible for seasonal outbreaks. Vaccination is an effective way to prevent infection and reduce the severity of symptoms. The flu vaccine is updated annually to match circulating strains, making it important for individuals, especially those at higher risk, to get vaccinated each year.