by Lesley Allen

Created on: January 29, 2009   Last Updated: January 31, 2009

Because the flu virus is constantly mutating, is it difficult to pinpoint the exact causes and origins of any flu epidemic, let alone the Spanish Flu epidemic of 1918. However, one person who has delved deeply into its possible causes is John Oxford, Professor of Virology at St Barts and the Royal London Hospital. His studies suggest that one particular combination of circumstances may have produced the pandemic (global epidemic) that claimed the lives of between 50 million and 100 million people.

The countries most affected were France, Britain, Germany, America and India. Contrary to popular thought, the first occurrence was recorded not in Spain but in Kansas. (It is because Spain was not involved in the 1914-18 war and its press was therefore free that it was able to report the first cases.)

The Spanish Flu, or Spanish Lady as it was sometimes called, is the worst pandemic in history because of the speed with which it took its victims. Whereas the bubonic plague killed millions over decades, the Spanish Flu claimed its victims in just one year. This happened in three separate waves; the first coincided with US soldiers arriving in Britain, the second occurred between September and December 1918 and the third was between February and April of 1919.

Professor Oxford's research suggests that the 1918 viral strain may have evolved in an army camp in Etaples, northern France. This camp had a population of around 100,000 soldiers, many weakened by the war, who would doubtless have bought live domestic birds and animals at local markets.

Small genetic changes occur in the composition of the flu virus in a process called 'antigenic drift'. It may be that during this process certain bird or animal flu strains combined with human viral strains to form a particularly deadly combination. The 1918 mutation may even have happened by means of yet a third species, for instance, domestic pigs. They are susceptible to both avian and human flu strains.

Flu had been observed before 1918 but this time the pattern was very different in that, particularly during the second wave of the pandemic, it was not only the very young and the very old who died, but the number of adult fatalities between the ages of 20 and 40 was out of all proportion to previous episodes.

Another unique feature of Spanish Flu was the apparent change in lung tissue. This condition, known as heliotrope cyanosis, left blue-black marks on the victim's face and ears and was caused by fluids flooding the lungs. It was, in fact, death by asphyxiation.

There were no vaccines available in 1918, neither were there any early warning systems. With the World War weakening so many people, and with large numbers gathered together in military camps and institutions, the possibility that a lethal cocktail was produced by an intermediary that was susceptible to both avian and human strains of flu virus cannot be dismissed. But the exact causes of the epidemic may never be known.

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