Flu is an acute febrile illness caused by the flu virus. Flu infects the respiratory tract and must be treated before complications begin to appear. Before you begin treating the flu, be sure to check that it isn't a common cold.
Normally the effectiveness of the influenza vaccine is how 66%. This year, however, the flu vaccine will be effective in 55%, because it is well combined with a type of influenza virus (H3N2)