The most resistant birds are the wild ones, who shed the virus in their organism and then spread it to poultry. Chicken, ducks and turkeys get infected if they get in contact with discharges from infected birds, infected water, and infected vehicles. The markets of live birds are also responsible for the virus's spread.

In 1983?1984 in the US another virus affected poultry. The H5N2 virus was low pathogenic but during 9 months it mutated and became highly pathogenic. During that epidemic 13 million birds died or were destroyed.

The virus can easily spread in the area if a contaminated bird is left to roam freely; if it drinks water from the place other birds drink, this way contaminating the water. Cars can spread the virus also from one place to another if they are not disinfected properly. Shoes, cages and clothing are also a way of spreading the virus.

This is why the infected farms need to be put under quarantine and the exposed flocks to bird flu need to be destroyed, to prevent the virus from spreading to other farms and other parts of the country.

This virus is in a continuous genetic development and as time goes by our treatment options become more and more restrained. Scientists need to move fast in finding an effective vaccine against bird flu, because the viruses have the ability of changing their status and of developing very fast, gaining even the possibility of transmitting themselves from one person to another.

The strain virus can swap or ?reassort? genetic materials and merge with another virus. This can lead to a more pathogenic form of a virus and can affect humans if the new virus contains genes from a human influenza virus. This will also cause a transmission of the disease from human to human.

Until now scientists knew that the mixing between bird flu virus and human flu virus can be made if both viruses are found during the same time inside pigs. But now it seems that humans can also become mixing vessels for viruses.

Normally the bird flu virus only infects birds and pigs but in 1997 in Hong Kong human cases of infection were registered. 18 people were affected and 6 of them died.

Humans can get infected if they get into close contact with ill birds. People who transport poultry, who feed them and clean the place the birds live in, are exposed to the virus if the birds are infected. Eating cooked chicken meal is not dangerous as the virus gets inactivated at heat.

In order to prevent a pandemic, governments decided to destroy all birds that got infected, to disinfect farms, cars, cages and any other object that could pass the virus from one place to another.