It is interesting to note that there are several similarities between the ‘Swine flu’ threat and the ‘Spanish flu’:
- Both were caused by an H1N1 virus that originally came from birds, but probably was transmitted to humans via pigs in America.
- Both caused relatively mild disease and little mortality in the first months of their appearance.
- The main burden of disease and mortality were found in relatively young people.
A clear difference between both pandemic events was that the “Spanish flu” eventually became much more virulent, harbouring several mutations that are associated with high virulence. Furthermore the introduction of the ‘Spanish flu’ happened in the absence of an already circulating seasonal H1N1 virus.