H1N1 flu pandemic of 2009
The H1N1 flu pandemic of 2009, also known as "swine flu," emerged in the spring of that year, with its initial outbreak traced to Veracruz, Mexico. This new strain of the Influenza A virus, closely related to the historic 1918 Spanish flu, raised concerns about a potential global pandemic due to its rapid spread beyond Mexico, with the first U.S. cases appearing in California in April. The virus was identified as a triple recombinant of human, bird, and pig influenza viruses, prompting health authorities to respond swiftly with measures including travel advisories and temporary bans on pork imports in some countries.
Despite fears of high mortality similar to past pandemics, the 2009 outbreak ultimately proved to be less lethal than initially anticipated. By November, it was estimated that 15 to 20 percent of the U.S. population had been infected, but the overall mortality rate was comparable to that of typical flu seasons. Interestingly, the pandemic disproportionately affected younger populations, particularly those under eighteen, while older adults exhibited significant immunity. This led to recommendations prioritizing vaccinations for children and adolescents. Ultimately, the estimated global infections reached around 60 million, with approximately 12,000 deaths reported across 74 countries, highlighting the complexity and varied impact of the pandemic.
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H1N1 flu pandemic of 2009
The Event: Global outbreak of a new strain of influenza, the H1N1 virus
Date: March 2009–May 2010
During the spring of 2009 a new strain of influenza virus appeared which was similar to the 1918 influenza outbreak that had killed tens of millions of people. The initial concern was that large percent of the population might be at similar risk of severe infection.
Early in the spring of 2009 an outbreak of influenza began in Vera Cruz, Mexico, in which the causative agent was identified as the H1N1 strain of the Influenza A virus. A similar strain was associated with the 1918 outbreak (known as the Spanish flu) which resulted in an estimated fifty million deaths worldwide. The H1N1 had briefly reappeared during the late 1970s in Fort Dix, New Jersey, and in northern China, but was locally confined. The rapid spread in 2009 within the Mexican population and beyond—the first cases in the United States were reported in California in April—gave rise to fears that a worldwide pandemic similar to that of 1918 might occur.
The 2009 virus appears to have been the result of a triple recombinant of human, bird, and pig influenza viruses, hence the popular designation as the “swine flu.” Responses by health authorities were rapid, including recommendations to limit travel to Mexico or other areas in which the virus appeared. In some instances the response by authorities to the swine flu bordered on panic; several countries banned the importation of pork products and Egypt ordered the slaughter of all domestic pigs.
The virus proved difficult to grow in the laboratory, so vaccines were in short supply during the first months of the outbreak. While the virus readily passed from human to human—by November an estimated 15 to 20 percent of the American population had been infected—it proved to be significantly less lethal than originally feared. The precise number of persons eventually infected worldwide is difficult to estimate because many people did not exhibit influenza-like symptoms and statistics were incomplete. The Centers for Disease Control and Prevention has estimated approximately 60 million were infected in 74 countries, with some 12,000 fatalities.
Impact
The level of mortality due to influenza as a result of the 2009 outbreak was no higher than that during normal flu seasons, and proved significantly lower than had originally been feared. In addition, the demographics of severe infection were different from the yearly outbreaks. The 2009 pandemic was largely confined to persons under the age of eighteen; few cases were reported among those over age sixty. Epidemiologists attributed these findings to significant immunity among older adults, the result of having been previously exposed.
Since the young were considered at greater risk, among the recommendations was that any vaccination program should give priority to those under the age of eighteen.
Bibliography
Barry, John M.. The Great Influenza: The Story of the Deadliest Pandemic in History. New York: Penguin, 2005. Print.
Dehner, George. Influenza: A Century of Science and Public Health Response. Pittsburgh: U of Pittsburgh P, 2012. Print.
Khiabanian, Hossein, et al. “Differences in Patient Age Distribution between Influenza A Subtypes” PLoS ONE 4.8 (2009): 1–5. Print.