Pandemic and epidemic influenza, 1830-1848.

Four major influenza epidemics were recorded between 1830 and 1848. The 1830-1831 epidemic may have originated in China; then and in 1833 influenza advanced westward out of Russia into Europe. In 1836-1837, influenza diffusion was largely north to south, and in 1847-1848 the disease swept through the Mediterranean to southern France and thence elsewhere in Western Europe. Each of the four epidemics spread rapidly and caused very high morbidity rates. Although case-mortality rates were always low, each epidemic killed thousands of people, with most deaths being among the elderly. Many previous writers have described all four outbreaks as pandemics, but true pandemics, presumably caused by major new viral types, are clearly identifiable only in 1830-1831 and 1833. The status of the 1836-1837 outbreak is unclear, but there was no pandemic in 1847-1848.