![]() In a desperate effort to save its charge, the immune system recruits such a storm of cytokines that the lungs suffer oedema. The resulting fibroblast exudates clog the lungs’ alveolar sacs, where gas exchange takes place, and an acute respiratory disease syndrome results. Once infected, the lungs’ vasculature becomes porous and fibrinogen-a protein involved in blood clotting-leaks into the lungs ( de Jong et al 2006). If much of H5N1's morbidity is distressing, its associated mortality is alarming. The respiratory attacks involved extensive infiltration of both lungs, diffuse consolidation of multiple infected loci, and lung collapse. Patients also suffered multiple‐organ dysfunction, including that of the liver, kidney, and bone marrow. These patients presented with high fever, later developing some combination of acute pneumonia, influenza‐like illness, upper respiratory infections, conjunctivitis, pharyngitis, and a gastrointestinal syndrome that included diarrhea, vomiting, vomiting blood, and intestinal pain ( Buxton Bridges et al 2000 de Jong et al 2006). The Hong Kong outbreak, first alerting the world to H5N1, infected humans with an influenza much more pathogenic than the relatively mild infections of other avian outbreaks that have intermittently crossed over into human populations. ![]() Most worrisome for human health is this strain's capacity for broad xenospecific transmission. Many birds also suffer infection in other organs, including the liver, spleen, kidney, and the brain, the last infection leading to ataxia and convulsion. Internally, infected poultry are marked by lesions and hemorrhaging in the intestinal tract and the trachea, with blood discharge from the beak and cloaca. The latter is characteristic of the cyanosis and oxygen deprivation suffered by many human victims of the 1918 pandemic. The clinical manifestations include swelling of the wattles and infraorbital sinuses, congestion and blood spots on the skin of the hocks and shanks, and a blue discoloration of the comb and legs ( Yuen and Wong 2005). The poultry infected with this version of the virus suffer more than the gastrointestinal condition typical of avian influenza. Despite another human death in January, the outbreak is broken. Authorities order the destruction of all of Hong Kong's 1.5 million poultry and block new imports from Guangdong, the mainland province across the Shenzhen River from which some of the infected birds had been transported. Hong Kong acts decisively on that information. By mid‐December poultry begin to die in droves in the city's markets and it now seems most humans infected had handled birds. The deaths spur panic in the city and, with the onset of the regular flu season, send many patients to the hospital worried their symptoms might be those of the new flu. Fourteen additional infections rapidly follow. Two weeks later, a teenager and two adults are infected. In November a 6‐year‐old is infected, recovering. Shocking too, the outbreak proves persistent. This appears the first time such a strain has jumped the species barrier and killed a human. The outbreak fizzles out, but 2 months later a 3‐year‐old boy dies of the same strain, identified as a highly pathogenic version of influenza A (H5N1). An outbreak of deadly bird flu sweeps through poultry on two farms. Influenza, 200 nm long, seems able to integrate selection pressures imposed by human production across continental distances, an integration any analysis of the virus should assimilate in turn. It appears the region's reservoir of near‐human‐specific recombinants was subjected to a phase change in opportunity structure brought about by China's newly liberalized economy. Particular effort is made to explain why H5N1 emerged in southern China in 1997. The novel contribution here is the attempt to integrate these with the political economies of agribusiness and global finance. ![]() In this article, I review H5N1's phylogeographic properties, including mechanisms for its evolving virulence. In contrast, little effort has been aimed at identifying influenza's social origins. Much attention has been paid to the virus's virology, pathogenesis and spread. Abstract: The geographic extent, xenospecificity, and clinical course of influenza A (H5N1), the bird flu strain, suggest the virus is an excellent candidate for a pandemic infection.
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