Interestingly, people also referred to the 1918 epidemic as 'the great grip', 'Spanish flu', and more accurately the Great Influenza epidemic. An estimated 500 million deaths worldwide, apparently. So terrible.
I would suggest removing Pearl Harbor (already covered in WWII), and adding the Johnstown Flood (2,208 deaths) and either the Peshtigo fire (1,500-2,500 deaths}, or more generally the 1871 Midwest Firestorm as was mentioned above.
And isn't the Attack on Pearl Harbor Part of WW2?