Glaciers Unlock Clues to Spanish Flu Pandemic

In less than one year, over a million people worldwide have perished from COVID-19, the novel coronavirus that has devastated countries such as the United States, Brazil, India and Italy. Researchers and policymakers have desperately tried to contain the spread of this deadly disease through development of a vaccine and implementation of preventative measures. Seeking a pathway out of the ongoing catastrophe, the world has turned to the last pandemic to cause such crippling and widespread damage—the Spanish Flu.

The Spanish Flu pandemic notoriously ravaged Europe and the U.S. between 1918 and 1919, occurring right at the tail end of World War I. One hundred years later, the global community is looking back to this tragedy for clues and insight to guide the eradication of 2020’s raging coronavirus. Climate science may provide additional insight into the deadliness and frequency of pandemics.

Climate researchers from Harvard University and the University of Maine have published a timely article in GeoHealth that explores links between a climate anomaly and the Spanish Flu pandemic. Their analysis of an ice core from the Italian Alps suggests that anthropogenic climate change exacerbated the Spanish Flu and, by extension, could play a role in the trajectory of COVID-19.

Ice core research allows scientists to metaphorically time-travel by recreating past climates. In a conversation with GlacierHub, Roxana Sierra-Hernandez, a postdoctoral researcher at the Byrd Polar and Climate Research Center who was not involved in the new study, described how researchers date ice cores and study trends in their structure and composition to gain an understanding of climates from eras long past. Trends in the ice can reveal periods of drought, heavy precipitation and temperature fluctuations.

In the new study, the scientists recreated a record of the chemical composition of an ice core sourced from the Colle Gnifetti glacier in the Italian Alps. They used lasers to melt a thin layer of ice, then analyzed resulting water vapor with a spectrometer.

GlacierHub spoke with lead author Alexander More, a climate scientist at Harvard and at the Climate Change Institute, and professor of public health at Long Island University, to learn more about his study. More explained that this was the first time that this laser system had been successfully applied to an ice core. With this system, More said “we’re learning to read glaciers like we read a book.” What makes this laser technology transformative is that it does not destroy the ice core, unlike other commonly used techniques. Instead it leaves nearly all of the ice core intact, allowing it to be saved and reused.

More and his colleagues combined temperature and precipitation records with analysis from the ice core to reveal a large climate anomaly, marked by low temperatures and extreme rainfall, between the years 1915 and 1920. Analysis from the ice core also revealed chlorine and sodium, components of marine sea air, had increased dramatically in this period. Interestingly, these spikes corresponded to years during which the First World War and the Spanish Flu both occurred. For this reason, More and his colleagues began to explore the link between this climate anomaly and the mortality rate of the Spanish Flu.

More and his team report that deaths from the Spanish Flu peaked three times in Europe, in 1915, 1916 and 1918 — each time preceded by dropping temperatures, extreme rainfall and cold marine air sweeping inland during winter. This cold air was likely the source of the increased chlorine and sodium levels found in the ice core. With this study, More and his colleagues sought to discover whether the climate anomaly of 1915-1920 exacerbated mortality from the Spanish Flu. He said, “the answer was a categorical yes.”

Medical historians have previously documented that freezing temperatures and dramatic rainfall events contributed to the deadliness of the Spanish Flu. The geochemical record produced by the Colle Gnifetti ice core substantiated historical records of dramatic increases in precipitation falling upon WWI battlefields — a record that has been frozen in time via photographs of muddy, puddle-filled battlefields and trenches. This rainfall left soldiers more vulnerable to various environmental hazards and infections, and also created ideal conditions for the spread of the Spanish Flu.

Not only did low temperatures and increased precipitation weaken immune systems, they may have also changed the migratory patterns of mallard ducks, carriers of H1N1 otherwise known as the Spanish Flu. More explained that mallards transmit the disease by contaminating bodies of water they land in.

Speaking with GlacierHub, Sierra-Hernandez praised More’s study, stating “we need to do these types of studies and connect climate and health.” She explained how researchers can not only use climate data to understand human health but use human health to explain climate conditions. She referenced a previous study which revealed lead emissions decreased during periods of plague because of reduced human activity. Similarly, greenhouse gas emissions have been seen to decrease during periods of lockdown during the coronavirus pandemic.

As for More and his colleagues, they used climate data to explain a human health crisis. According to More, the climate anomaly identified in the Colle Gnifetti ice core may have been exacerbated by human activity. The explosions and human activities such as increased industrial processes during the war could have kicked an excessive amount of dust into the air. These dust particles could then initiate the formation of rain by acting as nuclei on which the droplets could form. More further explained how a blanket of dust across Europe would block solar radiation, contributing to the colder temperatures experienced during the climate anomaly of 1915-1920.

This evidence that clearly links human activity to increased mortality during a pandemic raises critical questions during the age of COVID-19. Noting that SARS-CoV-2, the virus that causes COVID-19, originated in bats, More criticized the way humanity continues to encroach on animal habitats. “The underlying message of this article is ‘stop harming nature and we’ll stop harming our health,’” he said.

It is difficult to predict exactly how anthropogenic climate change will impact future pandemics. However, researchers can make educated guesses. “I don’t think anyone would argue that instability is good for humans, animals or the environment,” said More. “We have survived for the last thousands of years because the climate has been relatively stable. But now we’re going into uncharted territory.” While uncertainty surrounds climate change and pandemics alike, studies such as the one conducted by More and his colleagues provide experts with more pieces of the puzzle.