Influenza - Flu
Influenza, commonly known as the flu, is an infectious disease that infects birds and mammals (primarily of the upper airways and lungs in mammals) and is caused by an RNA virus of the Orthomyxoviridae family (the influenza viruses). The most common and characteristic symptoms of influenza in humans are fever, sore throat, myalgia (muscle pains), severe headache, cough, and malaise (weakness and fatigue).
A cold and a 'stomach flu' are very different from a flu. Influenza can be far more severe than the common cold and can even lead to death. Influenza and the common cold are caused by very different viruses. Gastroenteritis is commonly called "stomach flu" or "24 hour flu"; but that is a misnomer as it is not connected with actual flu.
Flu rapidly spreads around the world in seasonal epidemics, killing millions of people in pandemic years and hundreds of thousands in nonpandemic years. It creates health care costs and lost productivity. Three influenza pandemics in the 20th century, each following a major genetic change in the virus, killed millions of people all over the world.
The world's current major influenza pandemic threat is H5N1; but it is at present mostly a flu in birds, not in people.
The term influenza has its origins in 15th century Italy, where the cause of the disease was ascribed to unfavourable astrological influences.
Evolution in medical thought led to its modification to "influenza di freddo", meaning "influence of the cold", which by the 18th century became the prevalent terminology in the English-speaking world as well.
History
"Influenza was first described by Hippocrates as early as 412 b.c., and the tiny virus has spent the succeeding centuries shifting, drifting and wreaking havoc.
The first outbreak may have occurred in the Late Bronze Age in Egypt, where human contact with pigs fish and water fowl may have encouraged the avian illness to cross the species barrier.
Humanity has been seeking ways to eliminate the threat since the first pandemic was recorded in 1580."
"The fact that flu is caused by a virus was a British discovery, made in 1933 by scientists of the Medical Research Council (MRC)."
The most known outbreaks are caused by antigenic shift, when two strains of influenza recombine forming a lethal new strain. The most famous outbreak (and the most lethal) was the so-called Spanish Flu pandemic (type A influenza, H1N1 strain), which lasted from 1918 to 1919, and is believed to have killed more people in total than World War I.
While the war casualties accumulated over several years, the pandemic took most of its toll over a period of weeks. Lesser flu epidemics included the 1957 Asian Flu (type A, H2N2 strain) and the 1968 Hong Kong Flu (type A, H3N2 strain).
Effects
Influenza's effects are much more severe than those of the "cold", and last longer. Recovery takes about one to two weeks. Influenza can be deadly, especially for the weak, old or chronically ill. Some flu pandemics have killed millions of people.
Most people who get influenza will recover in one to two weeks, but others will develop life-threatening complications (such as pneumonia). Millions of people in the United States (about 10% to 20% of U.S. residents) are infected with influenza each year. An average of about 36,000 people per year in the United States die from influenza, and 114,000 per year are admitted to a hospital as a result of influenza.
According to estimates by the World Health Organization, between 250,000 and 500,000 die from influenza infection each year worldwide. Even healthy people can be affected, and serious problems from influenza can happen at any age.
People age 65 years and older, people of any age with chronic medical conditions, and very young children are more likely to get complications from influenza.
Pneumonia, bronchitis, sinus, and ear infections are four examples of such complications.
The flu can make chronic health problems worse. For example, people with asthma may experience asthma attacks while they have the flu, and people with chronic congestive heart failure may have a worsening of this condition, that is triggered by the flu.
Flu in Nonhumans Bird Flu, Horse, Swine, and Dg Flu
1918 flu virus' secrets revealed BBC - September 28, 2006
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