Even the Spanish Flu epidemic of 1918-1919 was the second round of the first version that had mutated .... The first go-round in 1917-18 was not as severe as the second.
At least according to Wikipedia, the second round happened because of the way soldiers were treated during the first round, crowded close together in hospitals and trains, allowing the virus to find many hosts and thrive. Which just goes to show you how so often with these novel diseases, the attempts to cure them are fumbling, bumbling and make things worse. No one should ever assume the authorities have a clue what the right thing to do is during these pandemics. This is one of the best times to question authority.