Introduction
Bird Flu is a form of influenza, which is caused by a highly pathogenic subtype of the influenza A virus, called H5N1. The name H1N5 is based on two proteins that occur on the surface of the virus particles, hemagglutinin (H) and neuraminidase (N). Avian influenza is a respiratory virus which predominantly causes fever, coughing, sore throat, muscle aches, and in severe cases breathing problems and pneumonia, which can be fatal.
Infection is caused by viruses that occur naturally in birds, and normally only infect them. The H5N1 strain has adapted from birds, and can cause illness in humans and many other animal species including cat, pigs, tigers and leopards. The people who are most at risk from bird flu are those who come into direct with birds, either by handling poultry or wild birds, or by visiting live poultry markets. To try and limit the spread of avian influenza, there is currently a ban on the importation of birds and bird products from countries where the H5N1 strain has been isolated.
Since 2003, avian influenza has spread rapidly in poultry across 17 countries from Asia to Eastern Europe and the Near East. Human cases of bird flu have been reported in Asia, Africa, Europe, the Pacific and the Near East. The highest number of cases have been reported in Indonesia and Vietnam. The bird flu virus does not infect people easily, and infection usually occurs by direct transmission from birds. Transmission from person-to-person is very rare. When humans become infected with bird flu it is very serious, with up to 60% of cases results in death. Avian influenza usually affects previously health children and young adults, with the majority of cases occurring in people between the ages of 10 and 19.
Because avian influenza is a bird virus, people do not have a high natural, or pre-existing, immunity. This makes the threat of a world-wide outbreak (pandemic) very dangerous, because many people could die. A bird flu pandemic could only occur if the H5N1 virus became able to spread easily from person to person, allowing efficient and sustained transmission among humans. Viruses are very efficient at swapping information with each other, which means the H5N1 strain could learn how to infect humans more efficiently from other viruses. While the likelihood of this occurring is low, the risk remains eminent as long as the virus continues to circulate through the avian population, and come into contact with viruses that readily infect humans. Public health authorities closely monitor cases of avian influenza as a means of controlling the risk of pandemic. Authorities are most concerned about cases of human infection and any evidence for increased person-to-person transmission.