Avian Influenza

Avian Influenza (Bird Flu)

An influenza pandemic is a global outbreak of disease that occurs when a new influenza A virus appears or “emerges” in the human population, causes serious illness, and then spreads easily from person to person worldwide. Pandemics are different from seasonal outbreaks or “epidemics” of influenza. Seasonal outbreaks are caused by subtypes of influenza viruses that are already in existence among people, whereas pandemic outbreaks are caused by new subtypes or by subtypes that have never circulated among people or that have not circulated among people for a long time. Past influenza pandemics have led to high levels of illness, death, social disruption, and economic loss.

There are many different subtypes of Influenza or “flu” viruses. The subtypes differ based upon certain proteins on the surface of the virus (the hemagglutinin or “HA” protein and the neuraminidase or the “NA” protein).

Pandemic viruses appear (or “emerge”) as a result of a process called "antigenic shift,” which causes an abrupt or sudden, major change in influenza A viruses. These changes are caused by new combinations of the HA and/or NA proteins on the surface of the virus. This change results in a new influenza A virus subtype. The appearance of a new influenza A virus subtype is the first step toward a pandemic, but the new virus subtype also must spread easily from person to person to cause a pandemic. Once a new pandemic influenza virus emerges and spreads, it normally becomes established among people and moves around or “circulates” for many years as seasonal epidemics of influenza. The U.S. Centers for Disease Control and Prevention and the World Health Organization have large surveillance programs to monitor and “detect” influenza activity around the world, including the emergence of possible pandemic strains of influenza virus. (The Washington Times A21)

There are growing fears of an influenza pandemic as avian flu sweeps through poultry stocks across Asia. Already, a dozen people have died as a result of contracting the disease by direct contact with infected birds, and there are fears of millions of deaths worldwide if the disease begins to be transmitted directly from one person to another.

While there is some basis to these fears, they are almost certainly overstated. Avian flu is a major problem for chicken producers in east Asia, but a number of important barriers mean its effect on human health is likely to be relatively small.

Avian flu has caused the deaths of millions of birds that were either infected with the disease or culled because they were potentially exposed to the Influenza virus that causes the disease. The disease has devastated the poultry industry particularly in American countries.

Avian influenza is not a new phenomenon. The disease was first diagnosed in Italy over a century ago as the cause of “Fowl Plague”. Since then, a Type A Influenza virus has been identified as the cause of disease. All birds are susceptible to disease, although certain birds are more resistant against the virus. Domesticated poultry are very susceptible to the virus thus making Avian Flu a dangerous pathogen to have on the farm.

The avian flu first spread among humans in Hong Kong where it infected 18 persons in 1997, six of whom died. Hong Kong had to cull the entire population of 1.5 million birds to effectively prevent the deadly H5N1 virus from spreading any further. The latest outbreak in Southeast Asia in 2003-2004 has been much more deadly. The disease has caused the deaths of 33 people in Thailand and Vietnam, and since the H5N1 strain has emerged in 12 countries. The World Health Organization (WHO) has confirmed the presence of deadly H5N1 in Vietnam, Thailand, Japan, South Korea, Cambodia, Indonesia, China, Laos, and Malaysia. In all, some 200 million birds were killed or culled by the virus in this area. Since then, milder strains of the virus has been reported in Taiwan, Pakistan, the United States, Canada, where culling has also occurred to control the spread of disease and virus. (The Washington Times A21)

There are approximately 6 billion chickens and 850 million ducks in the Southeast Asia region, where the area accounts for approximately one-quarter of the world’s poultry trade. Two countries currently affected by the avian influenza outbreaks, China and Thailand, account for 15% of global poultry shipments. With such massive culling of birds, there has been a devastating economic toll on the poultry industries of affected nations. The problem compounds itself as embargoes

(bans) on exporting birds have been placed on these countries.

The Chinese Academy of Social Sciences reports that economic losses to the industry could exceed $12 billion. According to the WHO, “many of the countries