Wikipedia:VideoWiki/Influenza

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Influenza, commonly known as the flu, is an infectious disease caused by an influenza virus.

The most common symptoms include: high fever, runny nose, sore throat, muscle pains, headache, coughing, sneezing, and feeling tired.

These symptoms typically begin two days after exposure to the virus, and most last less than a week. The cough, however, may last for more than two weeks.

In children, there may be diarrhea and vomiting, although these symptoms are more commonly caused by the unrelated illness, gastroenteritis (otherwise known as the stomach, or 24 hour flu).

Complications of influenza may include viral pneumonia, secondary bacterial pneumonia, sinus infections, and worsening of previous health problems, such as asthma, or heart failure.

Influenza viruses are classified into four types. Types A, B, and C, affect humans. Type D does not, but is believed to have the potential for it.

Usually, the virus is spread through the air, from coughs or sneezes, over relatively short distances.

It can also be spread by touching surfaces contaminated by the virus, and then touching the mouth or eyes.

A person may be infectious to others both before, and during, the time they are showing symptoms.

The infection may be confirmed by testing the throat, sputum, or nose for the virus with a rapid test, although people may still have the infection even if the results are negative.

Frequent hand washing, or wearing a surgical mask, reduces the risk of viral spread.

Yearly vaccinations against influenza are recommended by the World Health Organization, for those at high risk.

The vaccine is usually effective against three or four types of influenza, is usually well-tolerated, but only effective for a single season, since the virus evolves rapidly.

Antiviral drugs such as the neuraminidase inhibitor oseltamivir, have been used to treat influenza, but the benefit to otherwise healthy patients does not appear to be greater than the risks, and no benefit has been found in those with other health problems.

Influenza spreads around the world in yearly outbreaks, resulting in three to five million cases of severe illness, and 250 to 500 thousand deaths. About 20% of unvaccinated children, and 10% of unvaccinated adults are infected each year.

In the northern and southern parts of the world, outbreaks occur mainly in the winter, while around the equator, outbreaks may occur at any time of the year.

Death occurs mostly in the young, the old, and those with other health problems. Larger outbreaks, known as pandemics, are less frequent.

In the 20th century, three influenza pandemics occurred.

The Spanish influenza in 1918 that resulted in 50 million deaths,

The Asian influenza in 1957 that killed two million,

and Hong Kong influenza in 1968, that resulted in one million deaths.

The World Health Organization declared an outbreak of a new type of influenza A, called H1N1, or swine flu, that resulted in a pandemic during 2009, and 2010.

Influenza may also affect other animals, including pigs, horses, and birds.