Neither of your claims check out. The black plague killed a higher proportion of the world's population, and the 1918 Spanish Flu was airborne, like other flus.
There are properly more people living in Washington DC than in Europe during the time of the plague.
Not at all. According to Wikipedia, the population of Europe before the plague peaked at 70-100 million, while the plague killed 25-50 million, still leaving the population over 20 million, possibly over 50 million. The population of Washington DC is 592,000; if you include the metro area, 5.3 million.