Similar to the current corona pandemic, the second wave of the influenza pandemic of 1918 was the more violent in many regions. With the help of historical sources, researchers have examined the reason for this and the role played by hesitant measures using the example of the Swiss canton of Bern. In doing so, they discovered remarkable parallels to the current situation.
The Spanish flu is considered to be one of the great pandemics in human history. The infection, caused by an influenza virus of the type H1N1, probably broke out in the USA in early 1918 and then made its way to Europe with US soldiers in the final stages of the First World War. There the flu spread quickly to the population, some of which lived under poor conditions. The first wave in spring 1918 was followed by a second wave of the influenza pandemic in autumn 1918. It quickly spread to Asia and claimed more lives in many places than in spring. In total, between 20 and 50 million people died in the wake of the flu pandemic, including a particularly large number of young adults between the ages of 29 and 40. It is estimated that around 500 million people were infected.
Second wave in sight
The current corona pandemic has also gone through two waves in most regions: After an initial increase in infections and Covid 19 cases in spring 2020, the number of cases fell in summer, and then in many places in autumn and winter 2020 again drastically and more strongly than before to rise. In view of the parallels to the flu pandemic of 1918, researchers led by Kaspar Staub from the University of Zurich and Peter Jüni from the University of Toronto have taken a closer look at the sequence and possible background of the two influenza waves using the example of the canton of Bern. In their opinion, this canton is a well-suited case study because it is large and spatially heterogeneous, was hit particularly hard by the Spanish flu and introduced mandatory reporting at the beginning of the pandemic in July 1918.
As sources for the study, the research team evaluated, among other things, the weekly cases of influenza-like illnesses reported to the cantonal authorities by municipalities and regions, which are accessible in the Bern State Archives. “This source is a real archive treasure and an excellent example of how data that is more than 100 years old can be relevant for the present,” emphasizes Staub. As early as 2015, he and his team had started to transcribe over 9,000 medical reports with more than 120,000 cases of influenza from 473 Bernese municipalities between June 1918 and June 1919 in order to then analyze them using modern epidemiological methods. They also reconstructed the official measures taken at the time to prevent the spread of the pandemic.
Reluctant action
The evaluation showed that there were not only differences in the number of cases of the first and second flu waves in 1918 – the official reactions to the pandemic were also different: in the first wave in July and August 1918, the canton of Bern took action relatively quickly, strongly and centrally, among other things he restricted meetings and closed schools. “We can see from the numbers that these official measures – similar to today – were associated with a decrease in the number of infections,” reports Kaspar Staub. After the first wave subsided, however, the authorities lifted all measures again in September 1918. Shortly afterwards, this encouraged a resurgence in cases and led to the second wave of the flu pandemic.
But when this second wave picked up speed in October 1918, the canton of Bern reacted, unlike in the first wave, only hesitantly. For fear of renewed economic consequences, he initially left the responsibility for renewed official measures to the individual communities – similar to what happened in neighboring Germany at the same time. “This wait-and-see and decentralized approach was fatal and made a significant contribution to the fact that the second wave became even stronger and lasted longer,” says Jüni. To make matters worse, there was a nationwide strike in Switzerland in November 1918, accompanied by numerous meetings and demonstrations. This also promoted the spread of influenza. Ultimately, the second wave was responsible for around 80 percent of the illnesses and deaths reported in the canton of Bern from the flu pandemic.
According to the scientists, there are clear parallels to the current corona pandemic in the course of the flu pandemic and the factors that led to a particularly strong second wave. The second wave in Switzerland began almost in the same calendar week in both 1918 and 2020, and the authorities’ hesitant reaction was similar in both pandemics. “Although there are also significant differences between the two pandemics, the growing parallels between 1918 and 2020 are remarkable,” says Staub.
Source: University of Zurich, Article: Annals of Internal Medicine, doi: 10.7326 / M20-6231