What is influenza?
"Influenza" or "real flu" refers to a disease caused by the influenza virus. There are different types of this virus (influenza A, B, C). The most common and most dangerous is the influenza virus type A. It is common around the world and it is constantly changing, which makes it difficult to prevent.
"Real flu" is usually transmitted by droplet infections. Usually, about 80 percent of those infected do not realize that they had an influenza infection.
The other 20 percent of flu patient often get sick abruptly, presenting chills and severe malaise. Symptoms such as fever and body aches follow shortly thereafter. In case of an uncomplicated course of infection, he patient gets better within a few days. Influenza can be diagnosed with a rapid test. Apart from conservation and more general measures intended to alleviate the so-called viral symptoms, there are also the so-called antiviral medicines, which act against viruses. The flu virus can be prevented primarily by an annual vaccination.
By the way: A "common cold" is normally not an infection with the influenza virus, but a common cold. The gastrointestinal flu has nothing to do with the flu virus either. These gastrointestinal infections are caused by different agents and lead to diarrhea and vomiting, for example.
Important note: This article contains only general information and should not be used for self diagnosis or treatment. It cannot replace a doctor's visit.
Causes and risk factors
The influenza virus is transmitted by droplet infection. For example, an infection may occur if a sick person sneezes and another person inhales these droplets.
Pandemic: influenza outbreaks can occur worldwide
Local waves of infection (epidemic) or global waves of infection (pandemic) with influenza viruses are localized again and again. The ability of the virus to change plays an important role and the human immune system can hardly put up with it in such cases. Flu viruses are transmitted by droplet infection, so they can easily spread in very densely populated areas. Certain risk factors, such as a weakened immune system, encourage the infection.
Epidemic, pandemic
Why the virus spreads so easily
The worst influenza epidemic was the Spanish flu of 1918-1919, which killed over 20 million people. This flu made more victims than the entire First World War. Type A influenza has long been the most frequent cause of epidemics and pandemics. An epidemic is when a virus frequently occurs in a specific region and only last temporarily. A swine flu outbreak is an epidemic which is not limited to a local area, but in several countries or even worldwide. The Spanish flu was such a pandemic.
Experience shows that an influenza epidemic appear about every two to three years. Two things help: the high infection rate and the continuous change of the virus. Usually, it comes shortly after the development of a good immunity against the virus because of a change of the virus, because the influenza viruses change by small mutations and attack important regions of the immune system. Advances in medicine enable improved treatment and diagnosis, but cannot mitigate the consequences of influenza epidemics significantly.
Two different influenza viruses infect the same cell and it can happen that they exchange genetic material and virtually mix. This mechanism contributes to the change of the virus. Influenza viruses can also affect animals (e.g. birds and pigs) and can be then transferred to humans. Thus, completely new types of viruses are created. Major changes of the virus result this way every 10 to 40 years, which can lead to epidemics. This can lead to many deaths particularly in countries where many people live in a small space and only poor medical care is available.
The important surface antigens are neuraminidase and hemagglutinin.
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