When the ‘new pandemic flu’ first appeared in 1918 there was no immediate cause for alarm. The disease was different to other strains experienced in the past – for example, it was unusually prevalent amongst young healthy adults. But most people affected by what would turn out to be ‘the first wave’ of the pandemic recovered.
The 1918 influenza pandemic was commonly referred to as ‘the Spanish flu’ but it did not originate in Spain. It was given the popular name by journalists when the Spanish King, Alfonso XIII, fell seriously ill with a form of influenza in May that year.
Evidence suggests that this ‘mild’ first wave originated in North America. Influenza was present in many countries in late 1917 and early 1918. According to influenza historian Geoffrey Rice, author of Black November, only a ‘well-documented’ outbreak in Haskell County, Kansas, in January–February 1918 bore all ‘the characteristics of a new pandemic flu – high attack rate, higher morbidity rate and greater mortality than is usual for influenza’.
The disease spread among recruits who entered Camp Funston in Kansas, then to camps in Georgia and South Carolina, and then rapidly across the Midwest.
American soldiers are also credited with bringing the disease to Europe, where the first cases appeared near the huge American transit camps at Brest and Bordeaux in early April. By June the first wave had spread across most civilian populations in Europe.
The first wave followed normal diffusion patterns and struck the southern hemisphere a few months later, becoming prevalent in New Zealand in September. By this time it had run its course in Europe and cases related to the more severe second wave were emerging.
The first New Zealanders affected by the second wave of the 1918 influenza pandemic were soldiers of the 40th Reinforcement on board the troopship Tahiti. On 22 August their convoy – which had called at Cape Town, South Africa, en route to Plymouth, England – refuelled at Sierra Leone, West Africa. None of the crew or soldiers went ashore as fever was reported to be raging. But locals came on board to coal the ship, and within days over half of the men on board fell ill. The final death toll exceeded 80.
The first cases of a more severe form of influenza emerged amongst British and French troops serving on the Western Front early in July 1918. By mid-August the second wave, ‘a highly infectious flu, with sudden onset and an alarming propensity for pneumonic complications’, was spreading rapidly in France.
This time Europe would be responsible for infecting North America. By late September the second wave was well established in most of major cities.
The second wave did not follow normal diffusion patterns, instead striking the southern hemisphere while the disease was still raging in the northern hemisphere.
In October, for example, the flu was at its worst in countries as far apart as South Africa, Japan, China, Peru, Greece and Italy. It is now thought that the worldwide death toll was as high as 50 million.
According to historian Geoffrey Rice, the puzzle of the simultaneous outbreaks in both hemispheres may be resolved:
When one follows the very rapid diffusion from a July epicentre in eastern France: the second wave did not peak everywhere at the same time but was spread over four months, allowing ample time for diffusion by sea and rail.
Through the systematic analysis of individual death certificates, Rice calculated that New Zealand's peak of mortality occurred on 23 November 1918. This date has proved useful in dispelling the belief that the RMS Niagara was responsible for bringing a deadly new influenza virus to New Zealand.