Flu virus: Deadly 1918 pandemic may be the source of today’s milder seasonal flu

Viruses sequenced from century-old lung samples in German and Austrian museums have make clear how flu can change over time

By Clare Wilson

At this time’s seasonal influenza infections could also be attributable to direct descendants of the virus behind the 1918 flu pandemic.

That pandemic was the deadliest illness outbreak of the final century, infecting a 3rd of the world’s inhabitants and inflicting as much as 100 million deaths. For comparability, the present covid-19 pandemic is assumed to have resulted in 15 million deaths by the tip of final yr.

A lot concerning the 1918 pathogen continues to be mysterious: scientists solely demonstrated that flu was attributable to a virus within the Nineteen Thirties, and few samples of the pandemic virus stay. A few of these we do have come from our bodies buried within the Alaskan permafrost that remained frozen till they had been dug up within the Nineties.

Now, extra mild has been shed by Thorsten Wolff on the Robert Koch Institute in Berlin, Germany, and his colleagues. The staff genetically sequenced viruses from 13 lung samples saved in museums in Berlin and Vienna, Austria, that got here from individuals who died from lung infections between 1901 and 1931. Three of the samples had been from individuals who died in 1918, and two of those samples had been collected earlier than the pandemic peak within the remaining months of 1918.

By evaluating the viruses from the 1918 samples with modern-day seasonal flu viruses, Wolff’s staff discovered that trendy viruses may have descended from the 1918 virus.

The researchers additionally in contrast the 2 samples of virus taken over the primary few months of the 1918 pandemic with two beforehand sequenced pandemic viruses that had contaminated individuals later in 1918 because the pandemic peaked. They discovered there had been modifications in a gene that encodes the nucleoprotein, a protein that surrounds the virus’s genetic materials.

Earlier work on cells suggests these mutations may assist the virus evade human immune system defences triggered by chemical compounds known as interferons, which goal the nucleoprotein. This means the virus advanced to raised dodge the immune system, says Wolff. “We all know that this was a very virulent virus,” he says.

For the last decade or so following the 1918 pandemic, deaths from flu decreased markedly, which may have been as a result of larger inhabitants immunity or the virus changing into much less virulent, says Wolff.

Journal reference: Nature Communications, DOI: 10.1038/s41467-022-29614-9