The Spanish flu pandemic is often viewed as a devastating follow-on to the horrors of World War I. In fact, the two were much more closely entwined.

Visitors to the UK may wonder why, in a nation bristling with monuments to World War I battlefield casualties, there are no specific memorials to the 225 000 civilians and 30 000 troops who perished in the 'Spanish flu' pandemic of 1918-19. This was no deliberate omission, I would argue, but rather reflected the contemporary view that the war and the pandemic were both part of the same unprecedented calamity.

Indeed, it is impossible to understand the origins and dynamics of the pandemic without reference to the wartime conditions that allowed it to take root, facilitated its spread, enhanced its virulence and magnified its suffering. At the same time, the three waves of the disease materially impacted upon the conduct of the war effort and significantly complicated efforts to achieve a 'return to normalcy' in early 1919. Far from being mutually exclusive, the Great War and the 1918-19 flu worked in symbiotic and destructive partnership.

The Great War created perfect conditions for flu to spread in Britain. British civilians and soldiers were anxious, strained, depressed, physically overtaxed and undernourished. Huge numbers of people were in transit, and there was unprecedented overcrowding in munitions factories, bureaucratic offices, public transport and frontline trenches. It is even possible that the new H1N1 strain may have originated on the Western Front itself (see left).

In turn, the ensuing pandemic hampered the war effort, causing up to 40 per cent absenteeism in many factories and mines, and inflating frontline sick lists. On the Western Front, flu helped thwart a major German assault on Ypres, and compelled the British 15th and 29th Divisions to postpone their operations. With influenza-related mortality reaching its peak in the first week of November 1918, it is conceivable that the pandemic played some role in the decision to conclude the war with an armistice.

So the influenza pandemic was not, as some have stated, a predominantly postwar phenomenon. And in focusing upon its mortality, they have neglected the impact of its astronomically larger morbidity. Though World War I has often been heralded as the first military conflict in which combat losses surpassed those caused by sickness, this is only true in respect to permanent losses (deaths) and not to temporary losses, which incapacitated millions more.

Sporadic record-keeping in wartime, and the failure to make influenza officially notifiable, meant that actual incidence was undoubtedly far higher than was officially reported. The disease was often confused with other conditions, and in the initial pandemic phase, when its nature was a complete mystery, cases were often recorded as 'PUO' (pyrexia of unknown origin), 'three-day fever', or given some other generic label. Mortality figures should also be upwardly revised, as virulent flu often paved the way for fatal complications, but was not certified as a cause of death.

There is, then, much still to be learned about the Great War and its associated flu pandemic. Reconsideration is owed to the plight of women during the pandemic, both as mainstays of the industrial workforce and as nurses, the unsung medical heroes of the pre-antibiotic age. Non-Europeans serving the British war effort and British prisoners of war are two other much-neglected groups whose experiences need to be recovered from the "forgotten pandemic". According to one contemporary, in a situation of total war against a common invisible enemy, they all "laid down their lives in the cause as truly as those who fell on the field".

Further reading
Barry JM. The Great Influenza: The epic story of the deadliest plague in history. New York: Viking; 2004.
Brown, R. Fateful Alliance: The Great War and the 'Spanish flu' pandemic of 1918-19. Forthcoming book.
Brown R. The Great War and the great flu pandemic of 1918. Wellcome History 2003;23.
Brown R, Oxford JS. Plague on the western front. London: Channel 4; 2003. Brown R et al. Flu: A medical mystery. London: BBC Radio 4; 2003.
Van Hartesveldt FR. The 1918-1919 Pandemic of Influenza: The urban impact in the western world. Lewiston: Edwin Mellen Press; 1992.