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.
    On October 24, 1918, the city's elected legislative body, the Board of Supervisors of San Francisco, realizing that drastic action needed to be taken with over 4,000 cases recorded, unanimously passed the Influenza Mask Ordinance.
    The wearing of face masks in public became mandatory on US soil for the first time.

    Adoption of masks

    After San Francisco made masks mandatory in public, an awareness campaign began.
    The city's mayor, along with members of the Board of Health, endorsed a Red Cross publicity blitz which told the public: "Wear a Mask and Save Your Life! A Mask is 99% Proof Against Influenza." Songs were written about mask wearing, including one ditty that featured the lyrics: "Obey the laws, and wear the gauze. Protect your jaws from septic paws."
    Warehouses were converted to house the infected people quarantined.
    Anyone found outdoors without a mask could be fined or even imprisoned.
    The campaign worked and other Californian cities followed suit, including Santa Cruz and Los Angeles, followed by states across the US.
    And it wasn't just America.
    On the other side of the Atlantic similar steps were being taken -- the Committee of the Academie de Médicine of Paris recommended the wearing of face masks in the French captial in early November 1918. So did Dr. Niven, the medical officer of health for Manchester, in northern England.
    In a case of history repeating itself, this week the mayor of Los Angeles asked people to wear masks when out in