Wikipedia:VideoWiki/Influenza

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

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

Timing of symptoms
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.

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

Causes
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.

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

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

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

Diagnosis
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.

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

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

Vaccine effectiveness
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
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.

Epidemiology
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.

Geography
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.

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

History
In the 20th century, three influenza pandemics occurred.

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

Asian influenza
The Asian influenza in 1957 that killed two million,

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

Swine flu
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.

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