The flu

The term flu is used to describe a host of illnesses, but few people understand the true symptoms and effects of this common illness.

Although the common cold is sometimes confused with influenza, it is a much less severe disease and caused by a different virus. Similarly, gastroenteritis is sometimes called "stomach flu" or "24-hour flu", but is unrelated to influenza.

The flu is a very specific contagious disease caused by viruses in the influenza family. The word influenza comes from Italian word influentia, which means ‘influence.’

Typically, influenza is transmitted from infected mammals through the air by coughs or sneezes creating aerosols containing the virus, and from infected birds through their droppings.

The flu usually puts sufferers in bed for about a week, then leaves them feeling weak for a few days. However, the 1918 influenza strain was much more severe, it killed 50-100 million people worldwide. 

Influenza can be transmitted by saliva, nasal secretions, feces and blood. Infections either occur through direct contact with these bodily fluids, or by contact with contaminated surfaces.

Flu viruses can remain infectious for over 30 days at 0°C (32°F) and about one week at human body temperature, although they are rapidly inactivated by disinfectants and detergents. Influenza viruses are very specific about the organs they attack. They infect their respiratory system, which includes the nose, throat, trachea (windpipe) and lungs.

Flu spreads around the world in seasonal epidemics, killing millions of people in pandemic years and hundreds of thousands in non-pandemic years. It is a serious problem for everyone. Each year flue infects up to 20 percent of Americans.

Three influenza pandemics occurred in the 20th century—each following a major genetic change in the virus—and killed tens of millions of people.

Two new strains of flu have recently emerged, The first new type of flu is called bird flu or avian flu. While the second one called swine flu of H1N1 emerged early 2009. The rapidly changing nature of influenza continually produces new strains. Several different strains are now currently infecting humans around the world.
The Flu