A new study by researchers from McMaster University and the University of Colorado Boulder has challenged the widely held belief that the 1918 flu pandemic disproportionately killed healthy young adults. The study, published in the journal PNAS, analyzed the skeletal remains of 369 individuals who died between 1910 and 1938, including those who died during the pandemic. The researchers found that the most susceptible to dying of the flu had exhibited signs of previous environmental, social and nutritional stress.
The 1918 flu pandemic: a global catastrophe
The 1918 flu pandemic, also known as the Spanish flu, was one of the deadliest infectious disease outbreaks in human history. It infected an estimated one-third of the world’s population and killed between 50 and 100 million people. The pandemic was caused by an H1N1 virus that originated in birds and mutated to infect humans. The virus spread rapidly across the globe, aided by the movement of troops and refugees during World War I.
One of the most striking features of the 1918 flu pandemic was its high mortality rate among young adults between ages 20 and 40, who normally have strong immune systems and low risk of death from influenza. This phenomenon has puzzled scientists for decades, and has led to various hypotheses, such as a cytokine storm (an overreaction of the immune system), a previous exposure to a different strain of flu, or a genetic susceptibility.
A new perspective from skeletal evidence
However, the new study by Wissler and colleagues suggests that these hypotheses may not be accurate, and that the 1918 flu pandemic did not kill healthy young adults at random. Instead, the study argues that the most vulnerable to dying of the flu were those who had already suffered from chronic stressors that compromised their health and immunity.
The researchers used a unique source of data: the skeletal remains of individuals from the Hamman-Todd Documented skeletal collection housed at the Cleveland Museum of Natural History. The collection contains detailed records of each individual’s age, sex, cause of death, occupation, and medical history. The researchers divided the sample into two groups: those who died before the pandemic (control group) and those who died during the pandemic (pandemic group).
The researchers examined the shinbones of both groups for signs of stress, such as lesions caused by inflammation or infection. They also measured the height and weight of each individual, as indicators of nutritional status and growth. They found that the pandemic group had significantly more lesions, lower height, and lower weight than the control group, suggesting that they had experienced more stress in their lives. Moreover, they found that these stress markers were more pronounced among young adults than older adults in the pandemic group.
The researchers concluded that these findings challenge the myth that the 1918 flu pandemic killed healthy young adults indiscriminately. Rather, they suggest that the pandemic exploited pre-existing inequalities and vulnerabilities in health and society, similar to what has been observed in the COVID-19 pandemic.
Implications for future pandemics
The study has important implications for understanding how pandemics affect different segments of society, and how to prevent and mitigate their impacts. The researchers argue that pandemics are not only biological events, but also social and cultural ones, shaped by human behavior and interactions. Therefore, they call for more interdisciplinary research that integrates biological, historical, and social perspectives on pandemics.
They also emphasize the need for more attention to the social determinants of health, such as poverty, malnutrition, sanitation, education, and access to health care. These factors can influence how people respond to infectious diseases, both individually and collectively. By addressing these factors, public health interventions can reduce the risk of infection and death from pandemics, especially among marginalized and vulnerable populations.