100 years: Knowledge of the Spanish flu enhances our preparedness for future pandemics
The desk is full of historical material to be searched thoroughly for clues that can inform about the burden and signature patterns of historical pandemics and this knowledge make us wiser about the pandemics we may face in the future.
The desk is tt备用网址 Lone Simonsen’s and she has been researching epidemics and pandemics for several decades, including the Spanish flu.
This year, it is 100 years since the 1918 Spanish flu was raging, and within a couple of years the pandemic virus killed up to 50 million people globally, corresponding to about 1-2% of the world's population. It is impossible to say exactly how many Danes died of the Spanish flu, but depending on the sources, the number lies somewhere between 6,000 and 12,000.
?It was the mother of all influenza pandemics and forms the basis for our understanding of how a severe pandemic could look in the future? she says. And there are still unresolved questions about it, including the young age of most victims.
Although the Spanish flu occurred 100 years ago, it is still important to research its patterns and propagation.
?The more we understand about the Spanish flu and about what happened at the time, the more we can understand what could happen in the future and how we can defend ourselves against the next pandemic? explains the professor from Roskilde University.
It is interesting that 100 years after such a major pandemic, there are still many loose ends to explore
Pandemics are caused by novel viral pathogens crossing over from animals, and is something that happens with regular intervals and must be taken seriously.
?We sometimes forget that in the not so distant past severe pandemics such as cholera killed up to 10% of the population in some Danish towns. That is one out of every ten people you know in just a couple of months. We don’t really see that kind of disaster anymore, but there is really no reason why it could not happen again in the future? explains Lone Simonsen.
Wisdom saved in unique Danish data
At RUC, Lone Simonsen works with Associate tt备用网址 in mathematics Viggo Andreasen and others in the interdisciplinary field between biology and mathematics. A postdoc from The Netherlands, Maarten Wijhe, has recently joined the team. Part of the work has focused on finding historical material in Danish archives, which is better and more detailed than what is available in many other places in the world. The research is done in collaboration with an international network of researchers from other fields such as geography, history, physics and demography.
?We have spent much time over several years in the archives and university libraries finding interesting figures and information. It is absolutely incredible what you can find in those archives. Because we have unique Danish data in the form of weekly returns tabulating how many patients were seen with various diseases and stratified by many age groups and gender. Using this material we have been able to discover a lot about what really happened in past pandemics. These data may seem old and dusty, but there's real wisdom hidden there” says Lone Simonsen.
She and her colleagues are using statistical and dynamic models to work out what characterizes a pandemic of the past, its so-called 'signature features'.
They examine mortality patterns over age, time and geography. The Spanish flu from 1918, for example, is characterized by the fact that young adults died at an exceptionally high rate, while people over 45 years of age were largely unharmed in Denmark. Then a similar pattern happened in the 2009 pandemic, this time with evidence of childhood exposure of older people to a similar virus.
?Our findings showed that the type of influenza in childhood determines whether a person is at high risk or protected in a future pandemic" she explains.
The Spanish flu in waves
Another discovery that Lone Simonsen and Viggo Andreasen made using Danish data, is that Denmark, Norway and some other countries experienced an early summer wave of the Spanish flu.
?You must have really detailed health data - which we uniquely have in Denmark - in order to spot the first pandemic wave, because there were not many deaths. But we were able to demonstrate the unique Spanish influenza “signatures” in the summer data. We demonstrated this by finding the “signature” young age distribution of those who died and the rapid spread.
Four months later the main pandemic wave occurred, and this was far more devastating and deadly. We have also examined data from other cities across Scandinavia and see that Norway also experienced a large wave of pandemic influenza in early summer 1918” says Lone Simonsen.
The fact that a pandemic comes in waves can affect how well the population resists it. This seems to have been the case in Denmark in 1918.
?The first wave in Denmark was relatively mild. We believe that this first wave naturally immunized people in advance of the severe autumn wave in October 1918. This may explain why Denmark had a lower mortality than many other countries”, explains the RUC researcher, emphasising that only 0.2-0.3% of the Danish population died, while the rate was 40 times greater in some other countries that had not experienced a first wave.
Her insight into the pandemic's different waves enable Lone Simonsen to offer a message to those responsible for pandemic preparedness around the world:
?If a new pandemic should occur, then I would say to those who fight the disease that their work is not over after the first wave. More waves will come, and the later waves may well be worse than the first. This is good news as it provides time for a public health response, for example allowing time for production and distribution of a pandemic vaccine. We should not assume that a pandemic is a tornado-like phenomenon. There is an initial shock followed by several after-shocks, and many deaths can be prevented in the second and third waves in the first years” she says.
In addition to her work with historical pandemics, Lone Simonsen also works on evaluating the benefits of global vaccine programmes. In collaboration with her colleagues, she also works on other serious diseases such as cholera and malaria, where knowledge about how these diseases were brought under control in Denmark in the 19th century could provide insights into how to control such diseases in contemporary low income countries.
Still more mysteries left
2018 marks the 100th anniversary of the Spanish flu, and Lone Simonsen travels around the world giving presentations on the great pandemic. During the year, she will lecture at meetings in the USA, Iceland, Spain, France and New Zealand, where she will give talks for researchers, doctors, students, organizations and others with an interest in fighting pandemics.
But although she can tell us a lot about the Spanish flu some key mysteries remain.
?For each question we solve, new ones arise. It is interesting that 100 years after such a major pandemic, there are still many loose ends to explore, even though we know a lot about the signature of the Spanish flu” says the professor.
Lone Simonsen already knows which archives she will delve into in the future. The next mystery to be investigated is to characterize the age cohorts of young adults that were at enormous excess mortality during the Spanish flu pandemic.
Lone Simonsen is a new professor of Population Health Sciences at the Department of Science and Environment. In the spring semester of 2018, she supervises bachelor projects on subjects such as smallpox, bioterrorism, tuberculosis and influenza epidemics.
Fact box:
Pandemics
An influenza pandemic is an epidemic caused by a novel virus transmitted from animals to humans, which spreads across several continents. A pandemic may be severe, like the Spanish flu was in 1918, or rather mild, as was the case in 2009.
Where and how the Spanish flu H1N1 virus arose is still debated in the scientific literature. Hypotheses include origin in the United States, France and China, but the global spread has been linked to troop movements that occurred during World War I. Exactly how and why is another unresolved key question that still surrounds the Spanish flu.
Sources: Gyldendal Den Store Danske, WHO, tt备用网址 Lone Simonsen