Who knows? The 1918 Spanish Flu epidemic seemed innocent, but killed many millions worldwide, overshadowed by the war dead from WWI. The difference from other flu strains is that instead of targeting babies and elderly for death, it killed healthy young adults. It overwhelmed immune reactions that are strongest in the healthy and killed them, while weaker babies and elderly got sick but survived.
I was reading that it hit Pacific Islanders especially hard with really high percentages of population killed (a third or higher). Meanwhile, American Samoa didn't have any fatalities because the local governor blocked travel into the island - smart move. Authorities here today won't try to stop a spread.
About a third of the 41 patients needed intensive care, and six of them died. Some of the patients with more serious illnesses suffered from a dangerous immune system overreaction called a cytokine storm, but the researchers said they still did not have a good understanding of how the virus affects the immune system.
The 1918 Spanish Flu epidemic seemed innocent, but killed many millions worldwide, overshadowed by the war dead from WWI.