Table 1.
Baseline characteristics of different pandemics.
| Pandemic(years andcommon name) | Reference | Causativeagent | Area Of emergence | Estimated reproductive number | Secondary attack rates (%) | Estimated case-fatality rate | Age groups most affected |
| 1918–1919(Spanish flu) | [6] | Influenza A (H1N1) | Unclear | 1.7–2.8 | - | NA | Adult, pregnant |
| 1957–1958(Asian flu) | [8] | Influenza A (H2N2) | Southern Chine | 1.8 | 18.5–26.8 | NA | Children, elderly |
| 1968–1969(Hong Kong flu) | [11] | Influenza A (H3N2) | Southern Chine | 1.06–2.06 | 15.0 | NA | Elderly |
| 2009(swine flu) | [18] | Influenza A (H1N1) | Mexico | 1.4–1.6 | 17,5 | NA | Adolescent, young adults |
| 2019–(COVID-19) | A Novel Coronavirus(SARS-CoV-2) | Wuhan, Chine | 5.7 | < 2 | 2.3 | Elderly |
NA: Not applicable.