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.