Everyone seems worried about bird flu. Is there reason for the concern? Why are governments doing about it? What exactly is bird flu? Does bird flu carry a risk to human health ? Here are some facts about bird flu. Avian influenza, or “bird flu”, is a highly contagious disease caused by viruses that normally only infect birds and, sometimes, pigs. Avian influenza viruses have, on rare occasions, crossed the species barrier to infect humans. That is the current concern.
In domestic poultry, infection with avian influenza viruses causes two main forms of disease. The so-called low pathogenic (less dangerous) form commonly causes only mild symptoms (ruffled feathers, a drop in egg production) and may not be noticed. The more dangerous form is much more serious. It spreads very rapidly through poultry flocks, causes disease affecting multiple internal organs, and has a death rate that can approach 100%, often within 48 hours.Which viruses are the cause this serious disease?
Influenza A viruses1 have 16 H subtypes and 9 N subtypes2. Only viruses of the H5 and H7 subtypes are known to cause the highly pathogenic form of the disease. However, not all viruses of the H5 and H7 subtypes are that dangerous and not all will cause severe disease in poultry.
What is understood as of today is that H5 and H7 viruses are introduced to poultry flocks in their low pathogenic form. The problem is that when allowed to circulate among many bird populations, the viruses can mutate, quickly, into the highly dangerous form. This is why the presence of an H5 or H7 virus in poultry is always cause for concern, even when the initial signs of infection are mild. Because there have been many outbreaks, and deaths in various parts of the world, government health agencies, remain on the alert.