Avian influenza is easily carried across national boundaries through the trade, transport and travel routes that criss-cross the globe, and the natural flight paths of wild birds. Since the outbreaks of the disease in 2003, more than 250 million birds have died or have been killed in an attempt to halt its spread. This has caused an immediate loss of income for hundreds of thousands of poultry smallholders, mostly in a number of Asian countries, but also in Africa and parts of Europe.
At the same time, dozens of people have died from the disease and many consumers have rejected poultry, hitting both small and large poultry producers heavily.
The origins of avian influenza and the reasons for its evolution are still uncertain, although some evidence indicates that the enormous growth in highly intensive poultry production systems with relatively low biosecurity has provided a favourable environment for the virus to evolve.
The higher demand for livestock products, especially in Asia, has fostered the intensification of poultry production, with many smallholders increasing their flock size without improving the biosecurity. Global poultry bird population stands at 18 billion today, up from 14 billion ten years ago. A large share of people in South East Asia live in rural areas with low incomes and widespread ownership of poultry, over 60 percent of the poultry population, making an estimated total of at least 136 million poultry owners in just five countries.
In Africa, backyard systems account for 70 percent of the continent's poultry production. Domestic duck populations in China and Viet Nam together comprise around 80 percent of the world duck population and have increased threefold over the past two decades. Concentration of over one billion ducks and geese, many of them kept in open systems, has provided an effective breeding ground for the myriad of avian influenza viruses circulating in the wild waterfowl pool.
Subsistence production in backyard flocks is associated with a high risk of virus exposure and therefore infection of humans. Birds search for food by roaming freely or scavenging and therefore are in contact with possibly infected wild birds.For instance, in China, most outbreaks (76 percent) have occurred in small-scale and backyard farms. Those farmers who keep chickens to sell often do so through live bird markets, which bring different species together in usually unsanitary conditions.
The 2003/04 outbreaks in Asia took time to control and therefore spread widely or recurred, resulting in the death or destruction of many birds. Direct losses were highest in Viet Nam (around 45 million birds, accounting for approximately 17.5 percent of the poultry population) and Thailand (around 30 million birds, 14.5 percent of the poultry population). In Viet Nam, where about 63 percent of households earn less than USD 2 per day, the loss of chickens poses a serious income risk for most backyard producers.