Of all the avian influenza viruses that are seen in both humans and birds the subtype H5N1 caused the largest number of infections in humans. This subtype leaded to severe diseases and even death. More than that, it is believed that the registered cases are a small percentage of the real number of people that carry the virus. The registered cases are considered the severe ones while the unregistered and unreported cases are believed to be milder and without complications.



The H5N1 virus does not affect humans easily and if one person is infected it is impossible to spread the virus to another one. That is why this infection remains a rare disease in humans. Even so, as we said before, it is the most common infection that is seen in both birds and humans. The most affected regions are Asia, some parts of Europe, the Near East and Africa. More than half of these people that were reported as being infected with H5N1 have died. Most of them were children or young adults and have developed the virus after getting in direct contact with infected poultry or surfaces.

Even if some cases prove that the virus spreads from human to human too, specialists try not to agree. For sustaining the cause we have to remember that in 2004 in Thailand a human to human spread of the virus was reported in a family resulting from prolonged and very close contact between an ill child and his mother. Recently in June 2006 it was reported that a family of 8 was infected. The first family member is believed to have caught the virus from an infected poultry. He spread the infection to all of his family members, direct or indirect. It was proved that this family did not spread the virus to other persons except their family members.

The specialists are concerned that these influenza viruses have the ability to change, to mutate. They are also worried about the fact that the bird flu virus could merge with another human flu virus and may develop a new highly contagious and fatal virus that can lead to flu pandemics.

The risk of a pandemic is high and no one can tell when it is going to occur. That is why experts around the globe are watching the H5N1 situation in Asia, Europe and other possible infected areas and prepare for the possibility of person to person spread.

No vaccine or certain treatment is developed for these problems. it is only known that the viruses are resistant to amantadine and rimantadine, two antiviral medications used for influenza. It is believed that oseltamavir and zanamavir would work in treating influenza caused by H5N1 but additional studies have to be done.