Frequently Asked Questions about the avian influenza

Avian influenza is an infectious disease caused by a virus for which at least 144 roots have been identified so far. Most of them appear in wild birds and, in a higher percentage, waterfowl; these are known as “Low Pathogenicity Avian Influenza (LPAI)” and do not have a significant impact on poultry. On the other hand, H5 and H7 subtypes can cause high mortality among domestic poultry and are known as “High Pathogenicity Avian Influenza (HPAI)”.

The HPAI type virus does not usually affect wild birds. It appears in crowded poultry farms where the hygiene conditions are poor. Later the virus can be transmitted to wild birds by contact with domestic poultry or their environment. HPAI subtypes cause mass mortality among wild birds too.

H5N1 is a HPAI strain of the avian influenza virus that appeared for the first time in Hong Kong in 1997. It probably evolved from a LPAI strain in poultry farms.

The conditions in which domestic and farm poultry grow (crowded spaces, mixed groups, contact with droppings) help the evolution and transmission of the virus. The recent series of outbreaks in South-East Asia is closely connected with places where a higher concentration of farm and domestic poultry are found which have been bred in poor hygiene conditions. Also domestic ducks have contact with a variety of wild waterfowl during the day and with other poultry in the region at fairs and in the markets.

Until now there has been no clear evidence to support this opinion but we can't ignore this possibility entirely. It seems that the spreading of the virus in South-East Asia is the result of transporting sick birds among farms. The locations in which the virus was isolated do not correspond with migration time and direction of wild birds.

Nevertheless the recent cases in Europe were identified in locations that overlap with migration trails (including the Danube Delta).

H5N1 virus was not isolated in healthy wild birds, but only in dead or extremely sick ones. This suggests that the virus is highly pathogenic and the birds affected by it will not be able to migrate. Also it is known that this virus' life cycle develops at temperatures lower than 20ºC and consequently the outbreaks that coincide with bird migration might re-emerge once the temperature drops in areas already infected.

4. What other ways are there to spread this virus if wild birds are not responsible for it?

There are several ways to spread the virus from one geographical region to another: transporting the birds (and their feathers) to different poultry farms, the trafficking of captured wild birds and the involuntary transporting of soil on shoe soles and vehicle tires. Each of these ways of spreading the infection plays a certain part in the epidemic, but until now all cases were triggered by domestic and farm poultry transport.

There is no evidence of people being infected by wild birds so far. Only farm personnel have been infected. The number of human infections has been very small as compared to wild birds and poultry epidemics, which shows that the virus is still affecting people on a much smaller scale.

Although H5N1 can cause serious problems to human health, it is difficult to be infected with the virus and, until now, there has been no evidence that it can spread from one person to another. The problem would become most critical if the virus were found to be transmitted from human to human.

In the past 100 years there were 4 A-type influenza pandemics that resulted in many deaths around the world. It is considered that these pathogenic strains are the result of a combination between the genetic material of influenza virus specific to birds and that of humans. Taking into account the recent frequent H5N1 infection situations there is a possibility of a new pandemic outbreak.

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