Influenza, commonly known as the flu or the grippe, is a contagious disease of the upper airways and the lungs, caused by an RNA virus of the orthomyxoviridae family. It rapidly spreads around the world in seasonal epidemics, killing millions of people in pandemic years and hundreds of thousands in non-pandemic years.

Since the 16th Centruy, when accurate recording began, each Centruy has seen an average of three outbreaks of pandemic influenza, occurring at intervals from 10 to 50 years. In the 20th Century, there were three influenza pandemics:

History of Outbreak

	1st Outbreak
-	1918-1919. Of all the 20th Centruy flu pandemics, the one that began in 1918 was the most deadly. The first outbreaks were detected in Europe and the USA and the infection travelled back and forward on ships carrying troops and then, by land and sea, to Asia and Africa. It is estimated that 20 - 40% of the worldwide population became ill and some 40 million people died.
	2nd Outbreak
-	1957-1958.. The outbreak began in February 1957 in China., by August 1957, around two million people were estimated to have died during the pandemic.
	3rd Outbreak
-	1968-1969. The virus was thought to have emerged in China and was first detected in Hong Kong. Around one million people were thought to have died worldwide.

	Current Situation
-	1997-current – Influenza outbreak (Avian Flu – H5N1) in Hong Kong, China, Vietnam, Indonesia, Egypt, Europe.

The current global attention is focused the H5N1 strain in the avian influenza which was detected in pigs in Vietnam in February 2004. A new variant of the disease could be both highly contagious and highly lethal in humans. Such a subtype could cause a global influenza pandemic.