Influenza

Influenza - the most famous, most well-known cause of acute respiratory disease in general and SARS in particular. The best-known - does not mean that the most common, occurring most often. In the list of causes SARS virus, which was built taking into account the incidence of disease, the flu will be only in fifth place.

The best-known - does not mean that the most difficult: there is a terrible, heavier, poopasnee.

The fame of influenza is associated primarily with its ability to cause epidemics. When every third inhabitant of a particular town is in bed when polklassa not come to school - it is clear that this situation is on everyone's lips, and the guilty are almost always believe the flu is, of course, the glory of the virus support.

Influenza is known to mankind since antiquity. Descriptions of the disease, is extremely similar to the flu, plus guidance on the fact of simultaneous disease many people found in the writings of Hippocrates himself. It should, however, recognize that medical science has a very long time there was deadlock on the way and was sure that the causative agent of influenza is not a virus, a bacterium. Only in 1933 was proved by the viral nature of the disease.

Unjustly accused of microbe bacterium was named "Pfeiffer's bacillus. The first and very reasonable doubt in its involvement in influenza occurred brand name viagra during the famous epidemic of "Spanish Flu" in 1918-1919. But as you know, smoke without fire. In relation to the influenza bacillus Pfeiffer's rehabilitated, but proved her involvement in many other diseases - otitis media, sinusitis, epiglottitis, and even meningitam1.

But back to the flu. What are the specific features of the flu?

Home - the ability to variability. That is, the virus may be the most fundamental way to change their antigenic composition. And this leads to the fact that a very large number of people is completely absent of any immunity, but immunity is not "general", but it is immune to this, a new, previously unknown variant of flu virus.

Scientists have identified three main types of influenza virus - A, B and C. The most fundamental difference is precisely the ability to change.

Thus, the influenza virus with a virtually stable. And once a refresher, a man nearly all his life has immunity, ie, the flu is only possible with the first meeting with him. But because the virus is widespread, it becomes clear that adults with the flu almost never get sick. This is the inheritance of children.

Influenza virus B varies, but in moderation. If influenza C - a disease exclusively of children, the influenza B - mostly children.

Influenza A - the most insidious, precisely, it is constantly changing, causing an epidemic.

Fundamental point: the severity of the disease itself has little to do with how the virus is called: influenza A or influenza B, although influenza C occurs, it's usually easier.

The media occasionally talk on the approximation of "the terrible flu epidemic, but it does not indicate that this virus causes the disease more difficult or more dangerous. "A terrible epidemic" - hence, approaching significantly changed the virus, the virus, to which the majority of the population has no immunity. Hence, the number of cases will be very large. In this, again I stress, are terrible epidemic - namely the number of patients, but not in the severity of the disease.
In order to understand how the concept of "variability", and the causes of epidemics, we make sense to talk about the more subtle and complex matter - about the structure of the virus.

Let's start with the fact that the influenza virus belongs to the so-called "dressed", or the shell, viruses - this means that the virus incorporates a structure, not all viruses of the inherent - the shell. Inside the shell there is the main protein of the virus - an M-protein. Varieties of this protein, in fact, determine: how the virus is called - A, B or C.

M protein is stable. In other words, all the viruses A M-protein is the same. Always the same. And all the viruses in the M protein is the same. Always the same.

But the internal, stable, equal protein antigenic list of hazards, unfortunately, does not end there.

Depart from the surface of the shell special processes that are similar to spikes. Each spike - a particular protein, the specific antigen. The human body produces a corresponding antibody, the proteins destroy thorns, the shell of the virus, destroy the virus itself. If antibodies are present in the blood - the disease does not arise.

There are two main protein spike. And each has its own name. Title, forgive, complex, but the man who invented it, obviously not counting on the fact that such terms are used in popular literature. The author would love to, and not used, but life forces.

Thus, the two main protein spike.

The first is called hemagglutinin and is denoted by the letter H.

The second is called neuraminidase, and denoted, respectively, with the letter N.

To date, medical science, we know of 16 types of hemagglutinin and 9 types neyraminidazy3. Each type of hemagglutinin given a personal number: H1, H2, H3, H4, etc. Similarly, neuraminidase: N1, N2, N3, etc.
Each had a specific influenza virus M-protein and very particular combination of hemagglutinin and neuraminidase. As a result of the flu virus gets name.

As the name mean?

• from the M-protein comes to the specific form of the virus - A, B, C.

· Combination of hemagglutinin and neuraminidase is written as: H1N1 or H3N2.

· More add geographic location where the virus was detected for the first time.

• And a year when it happened.

As a result, we have a beautiful and now quite friendly name:
Now back to the volatility.

Thus, the virus has surface proteins - hemagglutinin and neuraminidase. The molecules of these proteins in the so-called "point mutations" slightly, but constantly changing its structure. This process is called antigenic drift.

As a result of antigenic drift of the structure of the virus changes very slightly, but even those small, unimportant, insignificant at first glance, the changes enough to human antibodies have lost their specificity.
Variability of the influenza virus is not limited to antigenic drift. Very often, but there is a situation where different influenza Viagra to prevent impotence viruses exchanged between antigens and then there is a fundamentally new combination of H and N, combination, to which no one on earth has no immunity.

This unique form of variability, that may influence the emergence of new, previously unknown variant of flu virus, called antigenic Shift.

Currently accepted that the ability to antigens of shift has only a flu virus A5.

Now we have the opportunity to explain certain patterns that show differences in the incidence of various types of influenza virus.

Influenza C. As already mentioned, the virus hardly subject to change. Constantly and actively circulating among the population. Once a refresher, you can get immunity for life. Therefore, influenza C ill children only. It is clear that the epidemic can not, occur as isolated cases and small outbreaks in groups of children.

Influenza B. Because the virus is prone to antigenic drift (and we already know what it is), every year there is a new version of the moderately changed. This modified virus can cause illness in large numbers of people. Ill, especially children - are in fact with the virus have not yet met. Ill adults. Those who had previously suffered from influenza, ie, have a body though not specific, but at least some antibodies - those will suffer lung disease. Those who have been ill a long time, or sick, or lose immunity because of advanced age or other diseases - those hard to get sick.

Influenza A. The annual developments taking place practically under the same scenario that was written for influenza virus B. That is, there are new options, resulting in the same antigenic drift, and morbidity occurs with the same pattern: children - often adults - less and lighter, the elderly and the sick - seriously.

Sometimes it will be something that we have already written, but once again repeat - because of the extreme importance:

situation arises when different viruses are sharing antigens (antigenic Shift), and then there is a fundamentally new combination of H and N, combination, to which no one on earth has no immunity.

That antigenic Shift influenza A virus is the cause of not just the flu epidemic and pandemic influenza.

A flu pandemic - an epidemic that covers many countries and continents, in fact - the whole world.
Once appeared on earth a new type of influenza A virus spreads among humans and cause a pandemic. But after that the virus does not disappear. Continues to circulate in human society is the cause of sporadic cases of the disease. But since most people have to this type of virus antibodies have been the epidemic becomes impossible.

Nevertheless, the farther in time humanity departs from the pandemic, the less people among us with antibodies to a particular variant of the virus. It is understandable because, in 1959 (after the Asian flu pandemic) in the world inhabited by billions of people with immunity to influenza A (H2N2). Years passed ... The number of individuals with antibodies to A (H2N2), diminished. And again, you can expect from this virus epidemic.

One consolation is only one thing - if you really expect an epidemic of A (H2N2), the doctors and scientists know it is about this version of the virus, almost all: age and epidemiological characteristics of the disease, typical symptoms and possible complications. That is unpleasant to wait, but at least we know what to expect. But when a virus is basically a new reason to worry about more than real.
As soon as we're talking about symptoms, epidemiological features, etc., look at this in more detail.

Thus, the influenza virus circulated in all countries and all continents. The peak incidence usually falls on the cold (winter) months. Is largely due to more active, more intimate communication of people (children) in schools, kindergartens, transport. Again, the exchange of indoor air can not be compared with that in the warm season. Windows are closed, all struggling with drafts, to keep the heat is so active that the airing space is regarded as an attempt to freeze the others. The main way of transmission from person to person - air-drop. Coughing and sneezing, plus transportation and room with an absent air exchange, plus a crowd of people - a logical and predictable result: the rapid spread of infections and epidemics.

In the air, the flu virus retains its activity up to four hours. By the way, and there are certain characteristics - resistance of influenza A is higher than that of influenza B. But both viruses "like" low temperature - the optimum figure of about 4 ° C. Pronouncing the word "love", we mean that it is at that temperature the virus persists for a long time. At the same time, the ideal temperature for breeding - a human body temperature.

The virus in droplets of saliva and phlegm, after these drops will dry and settle, such as bed linen, retains its activity for about two weeks, and in room dust - up to five weeks!
At the same time almost all disinfectants can easily kill the flu virus and the standard wet cleaning using these tools - a great way of disinfecting the premises. And if you add ventilation and washing clothes - so a local victory over the virus is more than real.

The incubation period for flu - from one to three days. The patient is contagious for 24 hours before the first symptoms. This, incidentally, one of the factors that make it impossible to prevent the spread of infection by various travel restrictions and quarantine measures.

Onset of the disease is almost always sharp: that is, practically no such that today 37,5 ° C, 38 ° C tomorrow, the day after 39 ° C. As a rule, faster: an hour ago, kind of like everything was in order - and suddenly 39 ° C, chills and my head split.

Average duration of fever perioda6 - 3-5 days, but we must take into account the fact that the patient is contagious for 1-2 days and after normalization of body temperature.

Flu symptoms are not specific: ie, not the flu is nothing that can not be observed in other SARS. If we compare with the bulk of other viruses, there is a tendency that the temperature increase is more pronounced, occur more frequently myalgia, headache, runny nose is less pronounced. In other words, the main and most characteristic symptom of the flu - it's not a stuffy nose, cough and 37,5 ° C, a condition marked by the words "bad at all."

It is worth noting that the principal feature, now is not the flu virus, but the actual disease called "flu", is the dominance of general toxic syndrome over the defeat of the respiratory tract syndrome. Nevertheless, this fundamental feature attracts attention precisely on the first days of illness, as well as normalization of temperature and improve the general condition of the fore catarrhal phenomena (coughing, stuffy nose, etc.).