The highly pathogenic Influenza A virus subtype H5N1 virus is an emerging avian influenza virus that has been causing global concern as a potential pandemic threat. It is often referred to simply as "bird flu" or "avian influenza" even though it is only one subtype of avian influenza causing virus.
On the March morning in 1918, while the Great War still enveloped Europe, a company cook went to the infirmary at Camp Funston, Kansas, with flu-type symptoms. By lunchtime over 100 soldiers were filling the hospital. Two days later, over 500 lay dying.
Within a single week it had spread from Kansas to all 48 states and a couple of weeks later French civilians and military were infected.
That year the “Spanish Flu” pandemic swept the world, stemming from the H1N1 influenza A virus, and killed between 50 million to 100 million people during the 18 months of the pandemic.
In 1957, the "Asian Flu" outbreak claimed more than 100,000 lives. To blame was the H2N2 influenza virus. In 1968, the H3N2 virus was responsible for the loss up to 750,000 lives in the "Hong Kong Flu" pandemic.
In 1996, a strain of an avian influenza bird flu, called H5N1, was isolated in a farm goose in Guangdong Province, China; the virus was highly pathogenic.
1997: In Hong Kong, avian influenza A (H5N1) infected both chickens and humans. This was the first time an avian influenza virus had ever been found to transmit directly from birds to humans. During this outbreak, 18 people were hospitalized and 6 of them died.
This year quick action was taken. Hong Kong entire poultry population, about 1.5 million birds, was slaughtered, and many experts believed this aggressive culling prevented a wider pandemic.
In 1998, H5N1 is found in two more people in Hong Kong. One eventually dies. In 2003, 83 people are infected with the H7N7 strain, with one fatality. The epidemiological findings indicated that in 2003, a family traveled to the southern part of China where it is suspected that they acquired the virus.
In 2004, the H5N1 and H7N3 strains infected dozens of people in Vietnam and Thailand--and two in Canada. Many of these people died. In Japan it appeared in chickens, the frost time that country had experienced a bird flu since 1925.
In 2005, strains have been found to infect people in Vietnam, Cambodia, Indonesia, and Thailand. Around 60 people have died, and strains are being detected in animals now for the first time in such places as Romania, Greece, Turkey, Russia, and England.
H5N1 virus has crossed the species barrier to infect humans, and there is a little natural immunity to H5N1 virus infection in the human population continue to be of a great concern for human health.
Bird flu in history
