Study of 1918-1919 Outbreak Shows Spanish Flu Origin

A French study of the 1918-1919 influenza pandemic, which analyzed mortality rates in approximately three-quarters of the European population, has concluded that it is unlikely that the virus, often described as Spanish flu, originated in Europe.

Published in the May issue of Influenza and Other Respiratory Viruses, the research shows a high degree of synchronicity in the 14 countries studied, including Spain, with the flu peaking in October to November 1918.

The study was carried out by a team from INSERM, the French National Institute for Health and Medical Research.

Key facts highlighted by the research include:

-- Overall deaths increased by 86 percent in the 14 European countries studied during the 1918-1919 pandemic, with 1.98 million excess deaths recorded. When these figures were extrapolated to cover the 25 percent of Europe not covered by the study, the figure reached 2.64 million.

-- Excess mortality rates for the individual countries covered by the INSERM analysis were: Bulgaria (102 percent), England and Wales (55 percent), Finland (33 percent), Sweden (74 percent), France (66 percent), Germany (73 percent), Italy (172 percent), Norway (65 percent), Denmark (58 percent), Portugal (102 percent), Scotland (57 percent), Spain (87 percent), Switzerland (69 percent) and The Netherlands (84 percent).

-- Figures for the worldwide death toll remain very imprecise. A first American report in 1927 suggested that the main 1918-1919 wave was responsible for 21 million deaths worldwide. A revised estimate in 1991 put the figure between 24.7 and 39.3 million and another in 2002 set the death toll at up to 100 million to take into account the lack of data in a large part of the world.

The authors point out that the source of the 1918 pandemic remains unclear. A recent analysis of the 1918 H1N1 genome failed to single out a particular location. Theories put forward by various researchers include Asia, a British army post in France in 1916, the U.S. and Spain.

The first reported pandemic was in 412 BC and the first attributed to influenza was in 1580. Since then 31 influenza pandemics have been reported, with the five most recent being in 1889, 1900, 1918, 1957 and 1968. The 1918 pandemic was the most deadly in modern history.

Reference: Ansart et al. Mortality burden of the 1918-1919 influenza pandemic in Europe. Influenza and Other Respiratory Viruses 3(3), 99-106. (May 2009).