The bird flu, also known as avian influenza and H5N1, is an infection caused by avian influenza A. Bird flu can infect many bird species, including domesticated birds such as chickens. In most cases, the disease is mild; however, some subtypes can be pathogenic and rapidly kill birds within 48 hours. Rarely, humans can be infected by these bird viruses. People who get infected with bird flu usually have direct contact with the infected birds or their waste products. Depending on the viral type, the infections can range from mild influenza to severe respiratory problems or death. Human infection with bird flu is rare but frequently fatal. More than half of those people infected (over 650 infected people) have died (current estimates of the mortality [death] rates in humans is about 60%). Fortunately, this virus does not seem to be easily passed from person to person. The major concern among scientists and physicians about bird flu is that it will change (mutate) its viral RNA enough to be easily transferred among people and produce a pandemic similar to the one of 1918. There have been several isolated instances where a person had been reported to get avian flu in 2010; the virus was detected in South Korea (three human cases), resulting in a quarantine of two farms, and in 2012, over 10,000 turkeys died in a H5N1 outbreak with no human infections recorded. Recent research suggests that some people may have had exposure to H5N1 in their past but had either mild or no symptoms.

    In addition, researchers, in an effort to understand what makes an animal or bird flu become easily transmissible to humans, developed a bird flu strain that is likely easily transmitted from person to person. Although it exists only in research labs, there is controversy about both the synthesis and the scientific publication of how this potentially highly pathogenic strain was created.