The duration of the incubation period of influenza is from several hours to 2 days with influenza A and up to 3-4 days with influenza B. The disease begins sharply, with the rise in body temperature to high values (39-40 ° C), accompanied by chills, general weakness, , muscular and joint pain. Fever reaches a maximum at the end of the first, less often on the second day of the disease.