The symptoms of human influenza were clearly described by Hippocrates roughly 2,400 years ago. Although the virus seems to have caused epidemics throughout human history, historical data on influenza are difficult to interpret, because the symptoms can be similar to those of other respiratory diseases.
The first convincing record of an influenza pandemic was of an outbreak in 1580, which began in Russia and spread to Europe via Africa.
In Rome, over 8,000 people were killed, and several Spanish cities were almost wiped out. Pandemics continued sporadically throughout the 17th and 18th centuries, with the pandemic of 1830–1833 being particularly widespread; it infected approximately a quarter of the people exposed.
The most famous and lethal outbreak was the 1918 flu pandemic (Spanish flu pandemic) (type A influenza, H1N1 subtype), which lasted from 1918 to 1919.
It is not known exactly how many it killed, but estimates range from 20 to 100 million people.
This pandemic has been described as "the greatest medical holocaust in history" and may have killed as many people as the Black Death.
The 1918 flu pandemic (Spanish flu pandemic) was truly global, spreading even to the Arctic and remote Pacific islands. The unusually severe disease killed between 2 and 20% of those infected, as opposed to the more usual flu epidemic mortality rate of 0.1%.
This is unusual since influenza is normally most deadly to the very young (under age 2) and the very old (over age 70).
The total mortality of the 1918–1919 pandemic is not known, but it is estimated that 2.5% to 5% of the world's population was killed. As many as 25 million may have been killed in the first 25 weeks; in contrast, HIV/AIDS has killed 25 million in its first 25 years.
The first influenza virus to be isolated was from poultry, when in 1901 the agent causing a disease called "fowl plague" was passed through Chamberland filters, which have pores that are too small for bacteria to pass through.
The etiological cause of influenza, the Orthomyxoviridae family of viruses, was first discovered in pigs by Richard Shope in 1931.
This discovery was shortly followed by the isolation of the virus from humans by a group headed by Patrick Laidlaw at the Medical Research Council of the United Kingdom in 1933.
However, it was not until Wendell Stanley first crystallized tobacco mosaic virus in 1935 that the non-cellular nature of viruses was appreciated.
The first significant step towards preventing influenza was the development in 1944 of a killed-virus vaccine for influenza by Thomas Francis.
This built on work by Australian Frank Macfarlane Burnet, who showed that the virus lost virulence when it was cultured in fertilized hen's eggs.
Application of this observation by Francis allowed his group of researchers at the University of Michigan to develop the first influenza vaccine, with support from the U.S. Army.
The Army was deeply involved in this research due to its experience of influenza in World War I, when thousands of troops were killed by the virus in a matter of months.
However, the economic impacts of past pandemics have not been intensively studied, and some authors have suggested that the Spanish influenza actually had a positive long-term effect on per-capita income growth, despite a large reduction in the working population and severe short-term depressive effects.
Other studies have attempted to predict the costs of a pandemic as serious as the 1918 Spanish flu on the U.S. economy, where 30% of all workers became ill, and 2.5% were killed.
A 30% sickness rate and a three-week length of illness would decrease the gross domestic product by 5%.
Additional costs would come from medical treatment of 18 million to 45 million people, and total economic costs would be approximately $700 billion.
Preventative costs are also high. Governments worldwide have spent billions of U.S. dollars preparing and planning for a potential H5N1 avian influenza pandemic, with costs associated with purchasing drugs and vaccines as well as developing disaster drills and strategies for improved border controls.
Backed by a request to Congress for $7.1 billion to begin implementing the plan. Internationally, on 18 January 2006, donor nations pledged US$2 billion to combat bird flu at the two-day International Pledging Conference on Avian and Human Influenza held in China.
In an assessment of the 2009 H1N1 pandemic on selected countries in the Southern Hemisphere, data suggest that all countries experienced some time-limited and/or geographically-isolated socio/economic effects and a temporary decrease in tourism most likely due to fear of 2009 H1N1 disease.
It is still too early to determine whether the H1N1 pandemic has caused any long-term economic impacts.
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Last Updated: Feb 1, 2011