2 Flu symptoms 2013 What is flu and How do you catch him

What is flu and the flu virus?

The flu is an acute infectious disease of viral etiology. Flu symptoms are fever, cough, headache and muscle aches. It spreads easily from person to person, it circulates around the world and can affect everyone - from the youngest to the elderly and cause epidemics and pandemics. Disease known since ancient times. There is evidence that humanity has experienced so far over 30 flu pandemics, and only in the last century, there were three. The most serious of these, so called. "Spanish flu", founded in 1918, has led to the deaths of 20-50 million people.

The flu virus belongs to the family Orthomyxoviridae, that there is only one race - Influenzavirus, including viruses causing disease in humans, mammals and birds. Some flu strains are species specific (infect only certain species, or only the people), but there are strains of flu that can spread from animal species to humans. Famous 3 types of flu virus - type A, type B and C. Influenza type C viruses, although similar in morphology differs from the other two types of the antigen and other basic properties. Influenza C occurs sporadically and causes respiratory disease with a slight leakage.
Viruses that cause seasonal epidemics are of type A and type B.
The most volatile are type A flu virus

The flu viruses are RNA viruses with a spherical shape. Their genome is divided into 8 separate fragments, which allows great opportunities for genetic variations. Wrapped in a lipid envelope containing two specific glycoprotein issued on the surface as "spikes" - hemagglutinin (H) and neuraminidase (N). Hemaglutininat serves for attachment of the virus to the cells. Neuraminidase facilitates the penetration of the virus into the cell, but also participates in the later stage of exit of the infected cell.



The flu viruses have developed many mechanisms to change its sheathoid glycoproteins, so as to prevent the body's defenses. Hemaglutininat most cosmetic and volatile component A virus neuraminidase also vary, but less intensively. There have been 16 types of hemagglutinin and 9 neuraminidase type. Designating influenza viruses type A reference established types N and H. There may be multiple combinations of different H and N, i.e. has the potential for many subtypes of influenza. In the past 50 years, most of the flu in humans were caused by strains with 3 subtypes of hemagglutinin (H1, H2, H3) and two types of neuraminidase (N1, N2). Contemporary indication of flu viruses and indicates where the virus was first isolated and year of isolation. Characteristic of influenza viruses is their ability to change. So they can overcome the body's defenses. Hemaglutininat is the most volatile component A virus neuraminidase is also changed, but less intensively. Small changes in the genes for hemagglutinin and neuraminidase are called antigenic drift. Drift occurs within a distinct subtype and may lead to a change in virulence. Large changes, called antigenic shift resulting from the rearrangement of the gene to be achieved between the 2 different strains of viruses likely conditions of mixed infection (e.g. infection of an organism with a human virus, and avian). That may result in a virulent strain which is more lethal and spread faster. They are responsible for a flu pandemic.

How do you catch the flu?

Flu viruses are spread by droplets through tiny droplets that are released when sneezing, coughing, speaking of people who are infected and are around us. Virus infection occurs after inhalation of these droplets. If the flu virus is not neutralized in the upper respiratory tract, to enter cells of the nose, throat, etc. and begin to rapidly multiply. Patient Virus removed from the beginning of the development of symptoms or within 24 hours before development. Viruses continue to be paid within 5-10 days. Young children shedding virus for longer. Patients with impaired immunity may secrete the virus several weeks to several months. Transmission of influenza viruses on contact time (by touch) is much rarer. Transmission of influenza from poultry or pigs to humans probably be achieved by a direct contact with infected animals. The risk is particularly high during the slaughter and preparation for consumption. Proper cooked meat poses no risk. Bird flu can also be spread through exposure to water and surfaces contaminated with bird droppings.

Throughout the year can be seen cases of flu. In an area annually observed seasonal ups of infection that are mostly among children in a time when they are clustered in schools and aerosol distribution mechanism is the most efficient. Autumn-winter seasonality is associated with the ability of the virus to survive better at low temperatures. Disinfectants destroy viruses in few minutes. Fly epidemics have occurred 1-3 years usually in season head. They are a result of the emergence of new strains.The flu pandemic covering the entire population of the world occurring in 10-20 years. The reason for this is the ability of influenza virus to modify and to avoid the immune system.