From understanding who is most at risk of illness to preparing for the next pandemic, there is a great deal to be learned from hundred-year-old death certificates.
One of the enduring questions of the 1918-20 influenza pandemic is why Indigenous populations in remote areas were more vulnerable than non-Indigenous people living in cities. Limited access to healthcare is a factor, but it doesn’t satisfyingly explain why the death rates in these populations was as much as eight times higher than non-indigenous ones.
Now, thanks to recently obtained data analysed by OsloMet Professor Svenn-Erik Mamelund, University of Missouri Professor Lisa Sattenspiel, and their team, we have clearer evidence that one of the key explanations is that remoteness limits exposure to earlier diseases.
The 1918 flu was especially deadly
The 1918 flu stands out as one of the deadliest influenza pandemics in history. Between two and five percent of the world’s population died in just a few years. As Mamelund puts it, "studying this historical event goes beyond scientific curiosity. It’s important to know how pandemics behaved in the past in order to understand what could happen in the future and prepare for it."
Mamelund says pandemics are connected across time. We need to know what to expect and how well earlier policy actions worked so that we can take a proactive stance toward the next pandemic.
The 1918 flu pandemic was difficult to manage in part because it didn’t affect the expected populations. We usually expect to see elderly people and young children hit hardest but in most places this wasn’t the case. Instead, researchers have found that across Europe and North America it disproportionately affected young adults.
However, Mamelund and Sattenspiel say that this was only true in cities. In indigenous populations in remote areas, the deaths are more evenly distributed and the elderly do make up a large portion of the deaths. The big question they are trying to answer is "why were Indigenous people across the world so much more vulnerable than people in cities?".
Studying this historical event goes beyond scientific curiosity. It’s important to know how pandemics behaved in the past in order to understand what could happen in the future and prepare for it.– Svenn-Erik Mamelund
Remoteness is a risk factor
There are many studies of disease, from even before 1918 through to the present day, that try to identify risk factors. Medical conditions - like heart disease, or tuberculosis, and even age - make someone much more likely to get seriously ill. We also know that lower social-economic status, substandard housing, and lower income lead to higher risk.
What we don’t know is how remoteness influences disease mortality.
Across the world, indigenous people - from Sami, to Pacific Islanders, to Alaska Natives - suffer many times more deaths from pandemics than non-Indigenous people living in cities. While this is well known among researchers, the reason for this discrepancy is still unclear. Mamelund and Sattenspiel think they’ve found the answer in records from the 1918-20 influenza pandemic.
Based on their new research, Mamelund and Sattenspiel hypothesize that the remote settings protect against the spread of viruses. According to Mamelund, “people living in urban societies are likely to encounter waves of various pathogens, but limited contact with outsiders means that people living in remote areas are less likely to encounter these pathogens. Even when a pathogen does reach them, the small communities (often home to less than 100 people) cannot sustain the spread of disease.”
While remoteness makes it less likely for diseases to arrive, when they do it can be absolutely devastating. Mamelund and Sattenspiel suspect that high death rates during the 1918-20 influenza pandemic may be a result of many remote Indigenous populations not having experience with earlier versions of the disease and therefore possess lower levels of immunity against the pandemic.
Tough life, fertile ground for research
The Alaska territory in the early 1900s was a strange and difficult place. Around 27,000 of the territory’s 57,000 inhabitants were Alaska Natives. The other 30,000 were non-Indigenous, drawn to the area by gold, furs, and the canning industry.
The non-Indigenous were mostly in their 20s to 40s, nearly all of them were men (around this time, the ratio of men to women in Alaska was 258 to 1), and over half of them returned to their home cities in the colder months.
These factors make the region great for studying pandemics. Both the Indigenous and non-Indigenous people in Alaska inhabited equally remote locations, faced a harsh climate, and had similar access to care. And yet, Alaskan Natives still experienced eight times higher mortality from the 1918-20 flu pandemic and had disproportionately high mortality among the elderly.
Professor Svenn-Erik Mamelund.
Seeking gold
It is this age discrepancy that Mamelund and Sattenspiel believe holds the key.
They are the first to seriously mine Alaskan death certificates from the time period for answers. “People look at cities at the expense of remote places like Alaska. Data on these communities is hard to find, so many people think the data doesn’t exist”, he explains. The death certificate data confirms the disparity in mortality rates that the team previously estimated from their work comparing anecdotes, various local reports, doctor notes, and diaries.
To unravel the mystery of why Indigenous populations in remote areas were more susceptible to the 1918-20 pandemic, the researchers calculated mortality over time and age, focusing on age-specific mortality.
It was difficult to identify deaths from flu because they could be listed as “flu”, or “pneumonia”, or several other complications. Instead, they looked at “excess mortality”, the number of deaths during the pandemic over an expected baseline number. This is the same method public health officials use today to tease out the number of deaths from COVID.
Mamelund found that both groups encountered virus in the same remote and cold setting. The higher mortality among elderly Indigenous people was the key finding. “Remoteness gave less exposure to flu in the past and that gives less immunity compared to people who have been living in cities or less remote areas”, he explains, “the non-Indigenous Alaskans must have encountered the virus in a different way in their origin cities in the past and brought their immunities with them”.
Remoteness gave less exposure to flu in the past and that gives less immunity compared to people who have been living in cities or less remote areas.– Svenn-Erik Mamelund
Lessons for the future
The cyclical nature of pandemics means that these lessons from history still apply today.
In the 2009 swine flu pandemic, for example, Indigenous people in North America, Oceania, and the Pacific again had three to eight times higher pandemic mortality than other populations.
Part of this difference is likely due to higher prevalence of medical risk factors for severe influenza outcomes among Indigenous people like diabetes and asthma, by higher risks of infection due to socioeconomic factors, and differences in access to health care.
However, the fact that Indigenous populations have lived, and often still live, in isolated places means that their inexperience with influenza almost certainly affects their immunity as well.
Mamelund and Sattenspiel's findings show us how we can protect these risk groups from the next pandemic.
“This idea of remoteness, less exposure and less immunity, is key to understanding mortality differences between remote indigenous and non-indigenous people in cities” says Mamelund.
Armed with this understanding, Mamelund suggests public health officials should make it part of their pandemic response plan. “When you know that indigenous people are at risk you should prepare for this to happen again, maybe they should be prioritized for vaccines”.
He encourages public health officials to consider this and include education and outreach programs to ensure that Indigenous groups accept vaccines when they are available. These well-administered vaccination programs will be the key to protecting vulnerable Indigenous populations from future pandemics.
Learn more
Lisa Sattenspiel, Svenn-Erik Mamelund, Sushma Dahal, Amanda Wissler, Gerardo Chowell, Emma Tinker-Fortel, Death on the permafrost: Revisiting the 1918-20 influenza pandemic in Alaska using death certificates, American Journal of Epidemiology, 2024;, kwae173 (academic.oup.com).
Centre for Research on Pandemics & Society (PANSOC)
