The Spanish Flu
The 1918 influenza pandemic (January 1918 – December 1920; colloquially known as the Spanish flu) was an unusually deadly influenza pandemic, the first of the two pandemics involving H1N1 influenza virus, with the second being the swine flu in 2009.[1] It infected 500 million people around the world,[2] or about 27% of the then world population of between 1.8 and 1.9 billion, including people on isolated Pacific islands and in the Arctic. The death toll is estimated to have been anywhere from 17 million[3] to 50 million, and possibly as high as 100 million, making it one of the deadliest epidemics in human history.[4][5] Historical and epidemiological data are inadequate to identify with certainty the pandemic's geographic origin.[2]
Infectious diseases already limited life expectancy in the early 20th century, but life expectancy in the United States dropped by about 12 years in the first year of the pandemic.[6][7][8] Most influenza outbreaks disproportionately kill the very young and the very old, with a higher survival rate for those in between, but the Spanish flu pandemic resulted in a higher than expected mortality rate for young adults.
To maintain morale, wartime censors minimized early reports of illness and mortality in Germany, the United Kingdom, France, and the United States.[10][11] Papers were free to report the epidemic's effects in neutral Spain (such as the grave illness of King Alfonso XIII).[12] These stories created a false impression of Spain as especially hard hit,[13] giving rise to the pandemic's nickname, "Spanish flu".[14]
Scientists offer several possible explanations for the high mortality rate of the 1918 influenza pandemic. Some analyses have shown the virus to be particularly deadly because it triggers a cytokine storm, which ravages the stronger immune system of young adults.
In contrast, a 2007 analysis of medical journals from the period of the pandemicfound that the viral infection was no more aggressive than previous influenza strains. Instead, malnourishment, overcrowded medical camps and hospitals, and poor hygiene promoted bacterial superinfection. This superinfection killed most of the victims, typically after a somewhat prolonged death bed.
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