Apparently is was also called "Flu Pandemic", it affected 500 million people all over the world and possible deaths were recorded between 50 million and 100 million, it was the worst disaster,
If you Google it you will find more information
My husband lost family members and I had a cousin who died, he survived the war but died due Spanish flu, he died in a military hospital and is listed on CWGC
Louisa Maud