In the 1918 flu pandemic, not wearing a mask was illegal in some parts of America. What changed?

Red Cross volunteers wore face masks during the flu pandemic of 1918.

(CNN)When the novel coronavirus pandemic hit Asia, people across the region were quick to wear masks, with some places like Taiwan and the Philippines even making them mandatory in certain scenarios.

But in the West, mask adoption has been far slower, with England's Chief Medical Officer Chris Whitty, for example, going so far as to claim mask-wearing is unnecessary.
Yet it hasn't always been the case that mask-wearing is an Asian proclivity.
    It certainly wasn't during the influenza pandemic of 1918, which lasted from January 1918 to December 1920, and infected one-third of the world's population, or about 500 million people, leading to about 50 million deaths -- about half a million of which were in the United States.
      There are many parallels between the two pandemics.
      While origin theories about the 1918 virus still abound, it was assigned a country specific name: the Spanish Flu. Globalization facilitated its spread as soldiers fighting in World War I took the flu around the globe. Then as now, warehouses were repurposed into quarantine hospitals. And an ocean liner with infected patients became a talking point.
      But one notable difference is that it was the United States which led the world in mask wearing.
      In October 1918, as San Francisco received the pandemic's second wave, hospitals began reporting a rise in the number of infected patients.