Concerns remain over the possible worldwide spread of the avian influenza (H5N1) that was very much in the news in 2005 and 2006 when the virus was spreading quickly through bird populations. Scientists feared that it would mutate into something that could transfer easily among people. Though a pandemic did not occur at that time, scientists still keep careful watch on this virus because the elements that led them to worry in 2006 are still in place. The spread of disease in the right environment could revive these fears. While the avian flu still presents a very real threat, the outbreak of the H1N1 (swine) strain of influenza A in the spring of 2009 has presented new worries.

The H5N1 influenza (avian) virus is a type A deadly strain. (The name is an abbreviation for a scientific description of its structure.) The disease has been wiping out chickens and ducks, primarily in Asia, for a good number of years. The first transmission to a human occurred in Hong Kong in 1997, and to date the disease appears to kill about half of the people who become infected. In comparison, the seasonal flu that strikes each winter kills only a small fraction of those who become ill, still about 36,000 Americans.

Thus far, the virus is being spread via migratory birds that do not seem to fall ill right away, so they can fly for a few hundred miles after infection. Then, for a week or so they seem to shed the virus into the lakes or marshes where they land. Other wild birds become infected, fly away, and further spread the disease. Domestic fowl, who encounter the wild birds or the water where they have been, become ill. In the domestic birds, the virus seems to be more virulent and kills quickly; it is thought that the virus becomes more virulent in populations that live in close quarters.

Until spring 2005, the virus was contained to Southeast Asia. By July, infected birds had carried it to Siberia, where the north-south flyway meets the east-west flyway. As a result, it has now spread as far as Turkey and Iraq. Since 2003, the World Health Organization (WHO) has reported that patients with the H5N1 virus have been identified in Vietnam, Cambodia, China, Indonesia, Thailand, and, most recently, Turkey and Iraq, with the number of people infected and dying increasing each year. Thus far, there have been about 140 human cases in Asia, according to WHO, and at least 15 cases in Turkey. The official numbers of cases and deaths include only those confirmed by the WHO, making it possible that others have sickened and died without seeking medical treatment. . .

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