What is Influenza or Flu?

Influenza or "flu" is an infection of the respiratory tract affecting millions of people every year. It is highly contagious disease which occurs mainly in the late fall, winter, or early spring. Influenza is spread from person-to-person through mists or sprays of infectious respiratory secretions caused by coughing and sneezing. Influenza affects all age groups and causes moderate to severe illness and complications such as pneumonia, hospitalization and in some cases it can lead to death.

The main way that influenza viruses are spread is from person to person in the form of respiratory droplets of coughs and sneezes known as "droplet spread." This can happen when droplets from a cough or sneeze of an infected person are propelled (generally up to 3 feet) through the air and deposited on the mouth or nose of people nearby. Though much less frequent, the viruses also can be spread when a person touches respiratory droplets on another person or an object and then touches their own mouth or nose (or someone else's mouth or nose) before washing their hands.

Most people who get influenza recover in one to two weeks, but some people develop life-threatening complications (such as pneumonia) as a result of the flu. People aged 65 years and older, people suffering with chronic medical conditions and very young children are more likely to get complications from influenza. Pneumonia, bronchitis, sinus and ear infections are three most common examples of complications from flu. The flu can make chronic health problems worse. For example, people suffering with asthma may experience asthma attacks while they having inflicted with flu. Person suffering with chronic congestive heart failure may have worsening of this condition that is triggered by the flu.

The flu virus can be spread starting one day before he or she falls sick. Adults can continue to pass the virus to others for another three to seven days after the flu symptoms start. Children can pass the virus for more than seven days. Usually symptoms start one to four days after the virus enters the body. Some people can be infected with the flu virus but have no symptoms. During this time, those persons can still spread the virus to others.