A/H1N1 from 1918-1919.
A/H2N2 from 1957-1963
A/H3N2 from 1968 through 1970.
H1N1 2009
Characterized by shift in the virus types, shifts to highest death rates among the youngest populations, successive pandemic waves, higher transmissibility than that of seasonal influenza, and differences in impact with varying geography.
The 1918 influenza pandemic lasted a little more than two years, and infected more than a half billion people, spreading to remote parts of the globe and causing more deaths than either World War I or World War II and possibly more than both combined.
Most deaths attributed to influenza infection occur concurrently with bacterial pneumonia at autopsy studies.
2009 pandemic H1N1 influenza A CDC study of 77 patients in the U.S., found concurrent bacterial infection in 29% of autopsied patients, with slighly less than half of the patients having Streptococcus pneumoniae infection.
Above CDC findings suggest the importance of pneumoccal vaccination for persons at increased risk for ppneumococcal pneumonia and need to recognize bacterial pneumonia in patients with influenza.
In the 2009 CDC study 22 cases of 77 confirmed H1N1 cases of death 22 suffered concurrent bacterial infections: 10 with S. pneumoniae, 6 with S. pyogenes, 7 with Stpahy aureus, and 1 with H.influenzae.