Flu (Influenza)

Denis Belanger, Pharmacist, Drug Information Specialist, Ottawa Valley Regional Drug Information Service

The flu is an acute respiratory infection caused by a variety of influenza viruses. Flu differs from the common cold, a respiratory infection caused by viruses, in several ways. Although the flu season runs from October to June, the months with the highest activity are January, February, and March. Outbreaks of flu usually begin abruptly. As it spreads through communities, the number of cases peaks in about three weeks and subsides after another three to four weeks. During an outbreak it can affect from 20% to 50% of the population. Most people who contract the disease will recover within a week, however for some people (i.e., the elderly, newborn babies, and people with certain chronic diseases) the flu and its complications can be life threatening.

Flu viruses are spread from person to person, usually by airborne droplets of respiratory fluids produced by coughing and sneezing. The viruses enter the body through the mucous membranes of the eyes, nose, and mouth. Symptoms usually appear after two to four days, and individuals are considered contagious for another three to four days after the first symptoms appear.

The classic symptoms of flu are headache, chills, and dry cough followed by body aches and fever. The fever usually declines on the second to third day. By the third day upper respiratory symptoms such as nasal congestion and sore through appear. A common cold rarely causes fever, headaches, and extreme exhaustion, and the aches and pains of a cold are much milder than those caused by the flu. Doctors usually diagnose the flu based on symptoms and whether or not the flu is epidemic in the community.

Treatment usually consists of bed rest, drinking plenty of fluids and taking medications like ASA (Asprin) and acetaminophen to relieve fever and discomfort. Children should not be given ASA due to the potential risk of Reye's syndrome. Recently, two new drugs - zanamivir (Relenza) and osetlamivir (Tamiflu) - were approved in Canada for the treatment of uncomplicated acute illness caused by influenza A and B viruses in patients that have been symptomatic for no more than two days.