San Francisco forced people to wear masks during the 1918 Spanish flu pandemic. Did it help?

A man in San Francisco poses for a photograph while wearing an wearing influenza mask during the 1918 Spanish Flu Pandemic. A man in San Francisco poses for a photograph while wearing an wearing influenza mask during the 1918 Spanish Flu Pandemic. Photo: OpenSFHistory / Wnp26.1205.jpg Photo: OpenSFHistory / Wnp26.1205.jpg Image 1 of / 34 Caption Close San Francisco forced people to wear masks during the 1918 Spanish flu pandemic. Did it help? 1 / 34 Back to Gallery

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Are masks effective controlling the spread of COVID-19? San Francisco's response to the 1918 Spanish flu pandemic, when the city government mandated that everyone wear masks, offers some clues.

The deadly Spanish flu killed an estimated 50 to 100 million people around the world. In San Francisco, influenza would infect over 45,000 people and cause the death of over 3,000 between Fall 1918 and Winter 1919.

Initially San Francisco, was slow to combat the virus.

The first reported case was on Sept. 24, 1918 when Edward Wagner fell ill after returning from Chicago. Dr. William C. Hassler, San Francisco's top health official, told the Examiner there was no cause for public worry after Wagner was quarantined.

But new cases continued to pop up. By Oct. 19, San Francisco had 3,733 infected people and 70 deaths.

ALSO: Social distancing is working. Here's why California's coronavirus peak is still projected for May.

Taking drastic action to slow the spread of influenza, Hassler ordered all amusement parks, theaters, movie houses, churches and prize-fight arenas closed, and all indoor meetings were prohibited. Public and private schools shuttered.

But the silver bullet in Hassler's holster was masks. He felt it was the most effective medium to mitigate the spread of influenza. If universally worn, Hassler told the Chronicle, the spread of the virus would be under control in a week.

So the Board of Health passed a resolution requiring all employees serving the public to wear gauze masks. Face masks were to be five-by-seven inches wide and made of four layers of fine gauze with string fasteners sewed to the four corners. The upper pair should tie around the back of the head, the lower pair around the neck. The board also urged the public to wear a gauze mask or chiffon veils.

The Red Cross stepped in to provide masks. They set up booths to sell masks to the public for 10 cents each. The Chronicle reported that Levis Straus and Company would manufacture masks, and provide one for every citizen of San Francisco, if needed.

Gauze masks were intended to be worn outside during the day. At night the health board instructed reusable masks be dipped in alcohol or boiled for five minutes and hung up to dry to be ready to use the next day.

The Red Cross placed an advertisement in the Chronicle urging the public: "WEAR A MASK and Save Your Life!" In the social pressure message of the day the ad continued: "Doctors wear them, Those who do not wear them will get sick. The man or woman or child who will not wear a mask is now is a dangerous slacker."

Photo: Chronicle Archive An advertisement from the Red Cross in the San Francisco Chronicle...

The Chronicle reported the Red Cross distributed 5,000 masks by noon. A second delivery of 10,000 masks in the afternoon sold out within a matter of hours. Overwhelmed by the response, the Red Cross asked women to make their influenza masks at home. "As the fullest resources of the Red Cross are inadequate to supply the demand for masks, it is the duty of every woman to provide her family with them," their statement read.

As the death count continued to mount steadily, the Board of Supervisors passes a resolution on Oct. 24 that wearing of mask in San Francisco was compulsory during the epidemic. City officials declared the penalty would be fines and the possibility of imprisonment.

In one day in October, 100 people in San Francisco were arrested for disobeying the mask order. "When the maskless ones found that the police meant business all manner of excuse were advanced for not wearing masks, the favorite excuse being that the mask had just been removed to permit of smoking," The Chronicle reported.

At the end of October, a full-page headline on the Chronicle lauded the mask order stating, "INFLUENZA MASKS PLAY BIG PART IN CURBING EPIDEMIC."

Photo: Chronicle Archive The San Francisco Chronicle Wednesday Oct. 30th, 1918 edition...

In early November new cases of Spanish influenza started to decrease slowly. City officials reported only 552 new cases on Nov. 2, with deaths below 100. Within a week, those numbers had fallen by half.

With new cases quickly dropping, Hassler declared the mask order a success while asking the public to remain vigilant. "The bars are not to be lowered an inch until this thing is stamped out. I believe San Francisco will be wearing masks for two months," he added. The health official credited the covers for preventing 20,000 cases of illness and 1,500 deaths in San Francisco.

By mid-November, with only a handful of new cases, restrictions on public gatherings ended and life in the city slowly began to return to normal. Hassler's two-month prediction did not come to pass, and the order to wear masks rescinded to take effect on Nov 21. That day at noon, sirens shrieked across the city — the signal for people to throw away their masks.

Minutes after the clock struck noon, the vast majority of people had taken off their masks, "laughing back at the sunlight and into one another's faces as if they had just made a great and delightful discovery," the Examiner reported.

A few were reluctant to take off their coverings, including a man working on Market Street. The Chronicle noted a dozen boys followed him shouting in a chorus, "Take off your mask." He refused their invitation.

After the mask rule was relaxed, the city was not entirely out of the woods.

MORE: How a quarantine saved everyone on Yerba Buena Island during the 1918 flu pandemic

An uptick of new flu cases in December prompted the mayor to ask, but not order, residents to don masks. He did not close businesses or prohibited social gatherings. Cases dropped once again, and people once again took off their masks.

In early 1919 new infections once again spiked. On Jan. 10, the health board reported 612 new influenza cases and 37 deaths, which led to Hassler to ask for reinstatement of the mask order.

Many San Franciscans were growing frustrated by the repeated calls to re-mask by government officials. Several people complained loudly against the order to mask at the Board of Supervisors meeting considering the issue. One man wrote the mayor complaining that San Francisco was the only city to compel residents to wear masks. "If Dr. Hassler feels inclined to wear a mask, let him do so, and as far as I am concerned, I hope he will have to wear one for the next five years," he wrote.

Despite their pleas, the board once again ordered the public to wear masks. However, many people fed up with wearing masks organized an "Anti-Mask League." They declared the mask order "contrary to the desires of the majority of the people," according to the Examiner. The organization asked for the law to be stricken from the books.

Hassler was against rescinding the mask order, believing it saved hundreds of lives. But public sentiment had turned against him.

With few new influenza cases, Hassler finally dropped his opposition, and anti-maskers got their wish. On Feb. 1, Mayor James Rolph, with the backing of the Health Board, declared the epidemic over and "the necessity for the wearing of the mask to have ceased."

Were masks useful saving lives in San Francisco during the pandemic?

In 2007 a study by the National Academy of Sciences of the U.S.A. found that the measures the city put in place, including face masks, to respond to the Spanish Flu reduced the mortality rate by at least twenty-five percent.

Inspired by San Francisco, a ship captain ordered all passengers wear masks from a trip from New York to England and there were no influenza infections on the journey.

However, according to a 2011 study from the National Institutes of Health, San Francisco's per-capita death toll ranked the 13th-highest of 66 large U.S. cities. The rate was significantly above the death rate of neighboring Oakland.

Another NIH study concluded the best, most effective way to limit deaths during a viral outbreak depends on a city quickly enforcing multiple social containment measures to contain an outbreak. "A primary lesson of the 1918 influenza pandemic is that it is critical to intervene early," explained Anthony S. Fauci, M.D. director of NIH's National Institute of Allergy and Infectious Diseases, and a prominent member of the White House Coronavirus Task Force.

In other words, a combination of factors (wearing masks, banning public gatherings, and enforcing social distancing) were likely responsible for ultimately taming the spread of influenza infections in San Francisco.

Online Photo Editor Douglas Zimmerman oversees SFGATE's Instagram and covers the Bay Area soccer scene on SFGATE's Beautiful Blog. View his latest stories and send him news tips at dzimmerman@sfgate.com.