Fragments of the virus responsible for the 1918 “Spanish flu” pandemic have been studied after laying locked in preserved lung tissue for over a century, revealing a number of new insights into the disease outbreak that wiped out well over 50 million people worldwide.
Genetic analysis of the influenza virus found in the tissue showed that the flu virus circulating in the milder first wave contained key genetic changes to the virus in the vastly more catastrophic second wave. Much like the ongoing COVID-19 pandemic, it looks like variants of the virus were a big problem during the 1918 influenza pandemic, but they didn’t have the scientific knowledge to understand them a century ago.
The study, which has not yet been peer-reviewed, was recently posted on bioRxiv. Scientists led by a team at Robert Koch Institute in Germany managed to get their hands on lung tissue from three people who died during the 1918 flu pandemic in Europe.
All three samples tested positive for the influenza A virus of the H1N1 subtype, the notoriously troublesome strain responsible for the 1918 flu pandemic as well as the Swine Flu outbreak of 2009 to 2010. The infected lung tissue came from a 17-year-old girl who died of influenza-related pneumonia in Munich in 1918, and two soldiers who died in Berlin, aged 17 and 18. As this suggests, part of the reason why the 1918 flu pandemic was so deadly was that it killed a surprisingly high number of young people. Remarkably, the team was able to sequence the complete genome of the virus found in the young woman from Munich and obtain significant parts of the genome from the other two samples.
This new research isn’t the first time scientists have managed to closely looked at the viral genome responsible for the 1918 pandemic. Back in the 1950s, scientists discovered the body of a woman who died during the “Spanish flu” pandemic in 1918 buried in the Alaskan permafrost. By 1997, scientists had even managed to recover enough viral RNA to sequence the 1918 H1N1 strain in its entirety. This genome, among a handful of other previously reported genomes, was also used in this new study as points of comparison.
Since the genomes of the virus in the new study came from the first wave of the pandemic, the researchers were able to gather some important insights into the virus as it surfed between the first wave of the pandemic and the second wave, which was responsible for about 80 percent of the reported cases and deaths.
Most crucially, the team managed to show that the second wave genomes featured mutations that could have helped the virus evade the human immune system, thereby making it more dangerous. The virus had essentially adapted to become more effective at infecting humans at some point within the early months of the pandemic. This mutated "variant" of the virus could potentially explain why the second wave killed drastically more people than the first.
As we’ve seen in recent months with the COVID-19 pandemic, newly mutated variants of the virus have some kind of links to the rise of cases and deaths seen around the 2020-2021 new year. While historical comparisons should always be treated with caution, it's apparent that the 1918 flu pandemic and the COVID-19 pandemic have shared many unpleasant traits.