Flu viruses can enter the body through the mucous membranes of the eyes, nose or mouth. After a person has been infected with the virus, symptoms usually appear within two to four days. The infection is considered contagious for another three to four days after symptoms appear. Once a person has the flu, treatment usually consists of resting in bed, drinking plenty of fluids and taking medication to relieve fever and discomfort. Flu complications generally result from bacterial infections in the lower respiratory tract.
Symptoms usually appear after the patient starts feeling better.
This brief period of improvement is followed by the sudden onset of high fever, shaking chills, chest pain with each breath and coughing that produces thick, yellow- greenish sputum. The flu season varies, but typically runs from November until April, with peak activity most often between January and March. Flu shots must be given annually, since scientists formulate a new vaccine each year from inactivated influenza viruses to deal with strains in circulation at the time. A strains of flu tend to affect more people because these strains change quickly and people are not able to develop immunity as well as they can to B strains. October is the optimal time to be vaccinated because it takes about two weeks for immunity to develop and provide protection.