Bird flu is a contagious infection caused by avian influenza viruses. These viruses are common in wild birds. The wild birds carry these viruses in their intestines but they almost never get affected or develop symptoms. Even so the wild birds spread the viruses among all types of birds. The domesticated ones develop a higher risk of illness than other birds and in their case the catch of the virus might lead to death.
Bird flu is highly contagious and will spread rapidly. The infected birds shed influenza virus in their saliva, nasal secretions and feces. The virus may be caught even if the birds get in contact with contaminated surfaces or secretions, not to mention direct contact with infected poultry.
The infection of domestic birds has two forms distinguished by the type of virulence that can be low or high. The low pathogenic form cause mild symptoms or may go undetected, while high pathogenic form spreads rapidly and leads to death in more than 90 % of the cases.
Influenza A viruses is known as having different subtypes because of the changes in certain proteins on the surface of the influenza A viruses: hemagglutinin ? HA and neuraminidase NA. We know 16 subtypes of HA and 9 subtypes of NA. Each combination of HA with NA represents a subtype of influenza A viruses and each one of it can be seen in birds.
In humans we only know three subtypes of influenza viruses: H1N1, H1N2 and H3N2.
The virus H5N1 is an influenza A virus subtype that occurs mainly in birds. This virus is very contagious and may affect humans too. The cause for infecting humans is direct contact with the birds infected with H5N1 or even with contaminated surfaces.
Of all the types of influenza viruses H5N1 is the most dangerous of all. There are known many cases of humans infected that ended with severe respiratory problems or even died. It was also reported a case in Indonesia of human to human spread of this virus. It was the case of an Indonesian family which members caught the virus and spread it among them. The virus was not spread to other families.
Scientists are concerned about the mutating of the H5N1 virus that may lead to easier spreading from one person to another. Because the cases of catching these viruses are rare there was no immune protection developed.
No one can tell when a pandemic might occur. That is why experts watch closely the situations in Asia and Europe preparing for the possibility of a influenza viruses pandemic.
Bird Flu Avian Flu
Specialists are unable to tell what is the virus that will cause the pandemic flu. More than that they are concerned about a flu pandemic, that will start, as they say, from the Far East. The problem will be how to prevent it from reaching Europe. They believe the virus will have a severe impact that will lead to a high number of cases and more than that to a high mortality rate.
In order to understand what are the risks of a bird flu pandemic we need to understand first what is a pandemic. We heard many times the terms flu epidemics which are normal and occur seasonally in every corner of the earth. We understand through epidemic a widespread disease that occurs in a community, population or area. A pandemic is an epidemic but at a much greater scale that spreads around the world and affects a high number of persons.
The history mentions three influenza pandemics occurred in the last century. First of it was the Spanish flu that began in 1918 and ended in 1919. Second we have to remember the Asian flu that lasted from 1957 to 1958 and the third one was the Hong Kong flu that lasted from 1968 till 1969. All three pandemics caused many deaths and huge economical and social disruption.
Influenza A is not the only group of flu viruses. It is true that influenza A was the cause of all previous flu pandemics and it is also true that influenza A viruses have the ability to spread from birds to animals and even humans. We should not forget influenza B and influenza C viruses that have the capacity to affect people but in milder ways than influenza A viruses.
The great concern of the specialists is that the virus H5N1, the subtype of avian influenza A could cause the next pandemic. The reasons they believe that are because of its already proved ability to infect people and cause severe health problems and because the virus capacity to mutate and acquire genes from viruses infecting other species.
Another great concern of the specialists is the two way possibility for the virus to either adapt or exchange genes with another human flu virus in order to produce a new virus capable of spreading incredibly fast through people.
In conclusion specialists affirm that in case of flu pandemic only a few people would have natural immunity.
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