Preview for Influenza in < Worldwide >:
[Note: GIDEON does not follow routine country reports on human Influenza, since the scope and nature of these data are diffuse, and often sporadic or inconsistent. Atypical infections and unusually severe outbreaks are summarized below and in the relevant country notes.]
Historical background:
The first known influenza epidemic was recorded in Europe during 1173 to 1174.
- A subsequent outbreak was recorded in 1580.
- Four pandemics were recorded during 1830 to 1848: 1830 to 1831, 1833, 1836 to 1837 and 1847 to 1848.
- 21 million deaths were estimated for an H1N1 pandemic ('The Spanish Flu') during 1918 to 1919. Some estimate the number as high as 40 million deaths.
- The "Asian flu" (H2N2, 1957) and "Hong Kong flu" (H3N2, 1968) pandemics each resulted in 1 to 4 million deaths.
- 21 million deaths were estimated for an H1N1 pandemic ('The Spanish Flu') during 1918 to 1919. Some estimate the number as high as 40 million deaths.
- The "Asian flu" (H2N2, 1957) and "Hong Kong flu" (H3N2, 1968) pandemics each resulted in 1 to 4 million deaths.
- An additional pandemic ("Russian Flu") was reported during 1989 to 1994.
- An additional 27 pandemics had been documented as of 2003.
- Excess deaths attributable to influenza in the United States numbered 603,600 during the epidemics of 1918 to 1919, 1957 to 1958 and 1968 to 1969.
- An additional 600,000 were estimated to have died in non-pandemic years during 1957 to 1990.
- A pandemic of H1N1 influenza involved over 200 countries (see below).
Influenza is transmitted through inhalation; however, direct contact with infected secretions has also been implicated.
- Acquisition of infection has been documented during international air travel.
- Patients remain infectious for 5 to 7 days, with the greatest degree of infectivity occurring during the first 24 hours of illness.
Influenza strains differ from one another according to the nature of two surface proteins: hemagluttinin (H) and neuraminidase (NA).
- Strains constantly evolve through a mechanism of reassortment, resulting in "antigenic drift" and "antigenic shift."
- Of the 15 H-subtypes, H-5 and H-7 are the most virulent to man.
Swine Influenza:
- 50 cases of swine influenza virus infection (most H1N1) were reported in humans during 1958 to 2005.
- A total of 46 cases of human infection by swine influenza viruses had been reported worldwide to 2008: 31 in the United States, 6 Czechoslovakia, 4 Netherlands, 3 Russia, 1 Canada and 1 Hong Kong. These figures include an outbreak (12 cases, 1 fatal) at a military facility in New Jersey, United States in 1976
- Two cases (non-fatal) of swine (H3N2) influenza virus infection were reported in the United States in 2009.
2009 to 2010 H1N1 influenza ("swine flu" ) - An outbreak was reported. Context : A pandemic of H1N1 Influenza virus infection occurred. Over 600,000 cases were officially-reported worldwide as of March, 2010. 16,713 fatal cases were reported to March 7, 2010.
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