Genes taken from the lungs of those killed more than 100 years ago, when mapped against the current H1N1 strain, suggested a genomic ancestor to our now-yearly flu, the team of international researchers found.
Scientists analysed 13 lung specimens collected from different people between 1901 and 1931 and carefully stored in historical archives of museums in Germany and Austria.
The century-old specimens included six samples taken from Spanish Flu victims in 1918 and 1919, during the peak of the killer pandemic.
This finding, scientists said, contradicted earlier thinking that H1N1 emerged through a process of reassortment, a phenomenon which involves the exchange of genomic segments between different viruses.
The H1N1 virus, once commonly referred to as swine flu, caused a flu pandemic in 2009.
In 2009, the global population had little immunity to H1N1 because it was new. The World Health Organisation estimating 100,000 to 400,000 died from the pandemic that year.
As the virus continued to circulate in people in Australia and around the world, it became a seasonal human flu virus.
The 1918 Spanish Flu caused the largest global pandemic catastrophe in the last century.
It had similarities to COVID-19, in that the virus spread worldwide, but the 1918 flu strain was far more deadly than the coronavirus, which emerged from Wuhan in China.
Spanish Flu peaked in the northern hemisphere autumn of 1918 and continued through the winter of 1919.
It is believed the virus reached Australia in 1919, causing up to 15,000 deaths, and infecting between between one-quarter and one-third of all Australians.
Australia’s population at the time was about five million.
While young children and the elderly were severely affected, the 1918 pandemic caused exceptionally high mortality in healthy people aged 20-40.
“We’ve had an eight-fold increase from March to April,” Professor Ian Barr, Deputy Director of the WHO Collaborating Centre for Reference and Research on Influenza, told 9news.com.au.
Lab-confirmed cases, which generally under-represent the reality, rose from 512 in March to 4663 in April.
“It’s quite a lot of influenza for this time of year,” Barr said.
“Normally, we don’t see start to see these sort of rises for another month or so.”
New South Wales, which leads Victoria and Queensland on April cases, should brace for a significant epidemic outbreak to hit this winter, he said.