Two experts on avian influenza say socioeconomic and cultural conditions in the developing world will ensure that the infection remains a threat to international health with a potentially severe toll on lives and livelihoods.
Avian influenza, or bird flu, is predominately found in birds such as waterfowl and shorebirds, but occasionally gets passed into poultry flocks or mammals, said Dr. Kristy Pabilonia, a veterinarian from Colorado State University, at the Third International Symposium on Agroterrorism. However, one strain of bird flu, H5N1, has jumped the species barrier into humans with fatal effects.
Humans who have caught the infection come from areas where birds and humans live close together. Unlike the developed world where poultry production is centralized commercially into large operations that have good biosecurity practices, most humans in the developing world get their poultry from small farms or birds raised and slaughtered in their backyards or in their villages. According to Pabilonia, more than 80 percent of residents in some areas of Asia, Russia, and Africa have "backyard poultry."
Because of the close proximity between birds and humans in these areas, one infected bird could infect the flock and increase the likelihood that humans contract the infection. When bird flu is discovered in backyard or village poultry, all of the associated birds need to be "depopulated," or killed, to stop the spread of the infection. But because villagers are dependent on these flocks for nutrition and income, Pabilonia says, there is a reluctance among villagers to report an infection. Sometimes they even move the flocks away from the village to evade detection, increasing the likelihood that the infection could spread to other animals and humans.
Bird markets, where people bring their live birds for slaughter and sale, are another source of infection. Generally, these areas are wet, which helps "virus survivability," says Pabilonia. When infected birds are discovered, farmers or owners typically sell off their flocks at bargain prices to minimize economic loss.
In Indonesia, where more people have died of H5N1 than anywhere else in the world, officials now try to get producers to stop bringing sick birds to market to halt the spread of the virus. Another solution, according to Dan Rutz, associate director of communication science at the Centers for Disease Control and Prevention's National Center for Preparedness, Detection, and Control of Infectious Diseases (NCPDCID), is to compensate bird owners for their losses so that they will report an infection to authorities who can cull infected birds. Countries like Ghana, India, and Vietnam do this already.
Humans are also exposed to H5N1 during the slaughter process, where they come into contact with infected carcasses and blood because they do not wear the proper protective gear. Pabilonia says there are many barriers to having people in constant contact with birds practice adequate biosecurity. The primary obstacle is economic. Pabilonia, who works in Indonesia, has assembled a rudimentary biosecurity kit for poultry handlers that costs around $7. The problem, however, is that most Indonesians live on $50 a month, so it's a tall task to ask farmers and sellers to spend a significant portion of their income on safety. Also, it can be difficult for even public health officials and veterinarians to wear personal protective gear when they have to deal with soaring tropical temperatures.
The infection is also spread by poor disposal methods. Both Pabilonia and Rutz told of seeing slaughtered birds floating in Indonesian villages' water supplies, increasing the likelihood that villagers would ingest the virus.
While difficult for humans to catch, the H5N1 strain of bird flu has a kill rate of 63 percent, according to World Health Organization (WHO) statistics. This kill rate, Rutz said, is worse than the Spanish influenza of 1918-19, which killed 500,000 Americans and possibly as many as 50 million people worldwide. The silver lining of H5N1 is that it is not only inefficiently transmitted from birds to humans, but it is even more inefficiently transmitted between humans.
What worries scientists and public health experts is that H5N1 will infect a human already infected with seasonal flu. The resulting convergence of the two strains of flu could combine together to form "a hybrid virus with the worst characteristics of both strains," says Rutz. This would likely result in a global pandemic that would overwhelm public health systems and disrupt economic and social support systems internationally.
Even if a hybrid strain of bird flu does not appear, international fear of H5N1 has already caused grave economic and social disruptions, as the recent outbreak in India shows. In February, the world's second largest exporter of eggs suffered a 50 percent drop in egg exports as fear of avian flu destroyed consumer confidence. Also in India, nine poultry farmers committed suicide as demand for chicken meat crashed amid fear of bird flu. The Indian government, reports Reuters, may have harmed its ability to contain the infection in West Bengal by offering paltry compensation for villagers' poultry flocks.
Up to this point, Rutz said, avian flu has not spread to the Western Hemisphere. If it did, consumer panic, both domestic and abroad, could decimate the U.S. poultry industry, valued at $26.8 billion in 2006, according to Pabilonia.
The one good thing about the rise of avian flu, Rutz said, is that it has led to widespread preparedness planning internationally. He says three outbreaks of pandemic influenza in the 20th century show that "another influenza pandemic is likely," even if it isn't linked to the current bird flu outbreak. Therefore, "it's prudent to plan," said Rutz.