The World Health Organization (WHO) recently sounded a global health alarm in response to a new threat that has been emerging in several regions, particularly Asia. This threat is the avian influenza, more commonly known as bird flu, which is an infectious diseases that affects only birds...until recently.
What exactly is bird flu?
Bird flu is an infectious disease caused by several subtypes of the Influenza A virus, which is known to affect birds, particularly migratory birds, ducks and chickens. Bird flu is also reportedly known to affect pigs and ducks although these animals only serve as carriers and are not known to exhibit symptoms of the disease. Migratory birds, in general, are equipped to handle the virus. They do not get sick but they have the ability to contaminate other birds in areas they migrate to. This is crucial factor in the spread of disease because migratory birds travel great distances, often from one country to another.
When did bird flu start?
Bird flu is not a new disease. First discovered in Italy in 1878, it was initially called fowl plague because it largely affected chicken livestock. However, it was only in 1955 that the Influenza A virus is the cause of bird flu. Since then, several subtypes of the Influenza A virus has been discovered in about a hundred bird species.
According to research, wild waterfowls, particularly ducks, are the most common carriers of the disease. The ducks, however, do not get sick from it. It was discovered that gulls, waterfowls and shorebirds are natural reservoirs of the bird flu virus. These animals appear to have developed antibodies to fight against the virus. Other bird species, however, have not developed this immunity to the virus.
Symptoms of bird flu
Birds with mild forms of avian influenza can exhibit ruffled feathers and poor egg production. Birds with advanced or extreme forms of the disease may show signs of excessive shedding, respiratory infections and a swollen head. When the disease worsens, death usually comes within 48 hours. This is because bird flu not only affects the respiratory systems of birds but also other tissues and organs, causing major hemorrhaging.
History of bird flu outbreaks
In the 1980s, bird flu outbreaks in chickens and birds occurred in Scotland, England, Canada, Germany, United States, Australia and Ireland. Again in the 1990s the same countries, with the exception of Germany and Scotland, had outbreaks. This time, Italy, Pakistan, Hong Kong, the Netherlands and Chile joined them. However, these outbreaks were small-scale; and highly pathogenic outbreaks are rare.
Then in 1997, a major outbreak of bird flu occurred in Hong Kong, which left 18 people infected and six people killed. In response to the outbreak, the Hong Kong government killed Hong Kong's entire poultry population, which was estimated at 1.5 million. Many believe that this rapid response to the bird flu outbreak was the best solution and helped avert it from becoming a pandemic.
To determine if a bird flu virus is highly pathogenic, eight chickens between four and eight weeks old are inoculated with the infectious virus. If 75 percent of the samples (six chickens) die within eight days, the virus is considered to be very pathogenic. In addition, a highly pathogenic virus will show a distinctive sequence of amino acids located at the cleavage site, the HA part of the chain.
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