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All about influenza (flu) influenza transmission causes of influenza influenza virus risk factors for influenza complications of influenza symptoms of influenza diagnosis of influenza treatment for influenza influenza prevention influenza vaccine (flu vaccine)

What's the influenza virus?

The currently circulating influenza viruses that cause human disease are divided into two groups: A and B. Influenza A has 2 subtypes which are important for humans: A(H3N2) and A(H1N1), of which the former is currently associated with most deaths. Influenza viruses are defined by 2 different protein components, known as antigens, on the surface of the virus. They are spike-like features called haemagglutinin (H) and neuraminidase (N) components. The genetic makeup of influenza

viruses allows frequent minor genetic changes, known as antigenic drift, and these changes require annual reformulation of influenza vaccines.

The influenza virus is in a class of viruses known as orthomyoxoviruses, with myxo referring to the fact that they infect mucus membranes. The most common types of influenza virus are A and B. Influenza A is the one usually responsible for the annual epidemics. Most people get multiple influenza infections during their lives. With many other types of infections - for example, mumps - having the disease once protects against a second infection because the body's immune system "remembers" the returning virus, attacks it immediately and rapidly eliminates it. With influenza, the virus usually has mutated (changed) somewhat since the first infection, but the change is enough to fool our immune system. So instead of immediately recognizing the invader, the immune system thinks it is a new infectious agent and the immune response is slowed. By the time the immune response is in full gear, millions of the body's cells already have been infected with the virus.

The influenza virus has become a menace to society and mankind. It does not stop to asks questions. It just infects, harms, and in some cases, kills. As humans we are confronted with problems that arise from this viral infection. We have yet to get the best of this virus, but only the future lies the fate of influenza. Influenza virus is probably the best known and most common virus among the human population. It mutates at an alarming rate and new strains appear on an annual basis. The occurrence of influenza peaks with the northern winter. This is because the population in the northern hemisphere is larger than that in the south and human habits - being indoors in warm damp conditions with lots of other people and then being outdoors in the cold - promote the spread of the disease. Once a person has had a particular strain they are immune to that strain subsequently. Sometimes this immunity extends to being effective or partially effective against future strains, but usually new strains of influenza are able to attack anyone. The disease has many symptoms. Some or all of these may occur: high temperature, fever, nausea, runny nose, sore throat, cough, congestion of the lungs and airways. In old people in particular, it can lead to serious respiratory diseases and secondary infections such as pneumonia, and this can kill.

Influenza viruses originate largely in the bird population. In the wild, such viruses can spread quickly when migratory birds gather for mating or flying to summer or winter habitats. But this does not explain how the virus enters the human population. The answer is that generally, it "leaps the species gap" in domestic birds such as chickens. In addition, some strains of influenza are known to have originated as hybrid chicken-pig viruses. Very often new influenza strains seem to originate in the Far East, where domestic fowl, pig and human populations are numerous and often live in close proximity to one another.

More information on influenza (flu)

What is influenza (flu)? - Influenza (flu) is a respiratory infection caused by one of the influenza viruses that typically is spread by air or by direct contact.
How is influenza transmitted? - Influenza is spread through contact with droplets from the nose and throat of an infected person during coughing and sneezing.
What causes influenza? - The flu is caused by three types (strains) of viruses - influenza A, B and C. Influenza A is responsible for the deadly influenza pandemics.
What's the influenza virus? - The influenza virus is in a class of viruses known as orthomyoxoviruses, with myxo referring to the fact that they infect mucus membranes.
What're the risk factors for influenza? - All people 50 years of age and older are at increased risk for serious illness with the flu, or in contact with those at high risk, and should receive vaccine.
What're the complications of influenza? - Influenza complications usually arise from bacterial infections of the lower respiratory tract. Pneumonia is the major serious complication of influenza.
What are the symptoms of influenza? - Influenza can cause a variety of symptoms. Typical flu symptoms include headache, fever, chills, cough and body aches. Intestinal symptoms are uncommon.
How is influenza diagnosed? - Diagnosis of influenza (flu) is based on typical symptoms of fever, chills, headaches, cough and body aches. There are a variety of tests to detect influenza.
What is the treatment for influenza? - The main treatment for influenza (flu) is to rest adequately, drink plenty of fluids, and avoid exertion. Amantadine and rimantadine are effective against influenza A.
How to control or prevent influenza? - The preferred treatment for influenza, and most viral infections is prevention. The prevention can be achieved through vaccinations.
What's the influenza vaccine (flu vaccine)? - Vaccination is the principal measure for preventing influenza. Influenza vaccinations are given to millions annually.
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All information is intended for reference only. Please consult your physician for accurate medical advices and treatment. Copyright 2005,, all rights reserved. Last update: July 18, 2005