1918 Today

Figure 1. Global travel time map from London, 1914

 Despite these transportation limitations, there was still considerable human movement one hundred years ago. By 1918, shipping and train networks were becoming well-established. The speed of spread during the 1918 pandemic also became supercharged due to World War I. Due in part to World War I, the 1918 pandemic spread surprisingly quickly, reaching London by June of 1918- just weeks after the presumed start of the pandemic (April 1918). Further historical evidence suggests the pandemic reached Sierra Leone through British warships by August 1918, and Nigeria and Kenya by September.

How did World War I impact the speed of spread?

• Increased international travel. During the summer of 1918 nearly 10,000 troops a day from the United States entered France.
• Crowded wartime living conditions increased transmissibility.
• Limited medical resources dedicated to war effort reduced the ability to help mitigate the pandemic.
• Government censorship inhibited the public from knowing the true severity of the pandemic.

The Present

How is human mobility different today?

• Increased interconnectedness and accessibility. The global flight network (Figure 2) has drastically increased connectivity between cities and allowed humans to reach areas previously inaccessible.
• Increased volume. In 1918, human population was 1.8 billion, today we are approaching 8 billion.
• Increased speed. In 1918, circumnavigating the globe took roughly 60 days, now it's less than a day.

Figure 2. Global Flight Network. OAG 2016. Color corresponds to the geographic region (e.g., Europe) of the origin airport

 To better understand spread risk, researchers can incorporate air travel, commuting, and migration travel patterns into a global disease spread model. These mobility models allow researchers to predict the probability of a disease being introduced to a new location. Based on Metabiota’s pandemic model, we observe a pandemic with similar characteristics to the 1918 pandemic would today reach more than half of all countries within five months of the start of the pandemic.

The Future

To better prepare for the next pandemic, Metabiota has created millions of simulations accounting for today’s risk of spark, spread, and preparedness. The pandemic influenza model demonstrates that pandemics with similar characteristics to the 1918 influenza pandemic would likely spread to over half of all countries within five months. Simulations with a greater speed of spread cause larger peaks of infections. A greater peak number of infections causes a greater demand of hospital beds at one time. Hospitals, which are often are at full-capacity in normal times, may not be able to keep up with the influx of demand to a 1918-like pandemic.

The problems posed by a higher peak number of infections goes beyond hospital beds. Metabiota’s absenteeism model, informed by first principles and accounting for fear-based absenteeism, indicates companies could expect peak worker absenteeism to approach 30% during a 1918-like pandemic. In today’s just-in-time economy, a high absenteeism rate could easily disrupt the interconnected global supply chain including medical supplies, antivirals, and vaccines. And in our ever increasingly interconnected world, quarantine and isolation to help mitigate the speed of spread becomes less economically feasible.

The Takeaways

• World War I helped create the "Perfect Pandemic" in part by increasing the speed of spread.
• If the 1918 influenza pandemic occurred today, the speed of spread would be noticeably quicker due increased interconnectedness, accessibility, volume, and speed.
• Today's travel dynamics can allow a pandemic to spread to many countries before a pandemic is even recognized increasing potential health and economic harm.