Many of the methods Americans used in 1918 to try to prevent the spread of the flu are similar to what people began doing during the COVID-19 pandemic: Close schools. Wear masks. Don’t cough or sneeze in someone’s face. Avoid large events and hold them outside when possible. And no spitting.

Health and city officials got the word out about these guidelines in all kinds of ways. In Philadelphia, streetcar signs warned “Spit Spreads Death.” In New York City, officials enforced no-spitting ordinances and encouraged residents to cough or sneeze into handkerchiefs (a practice that caught on after the pandemic). The city’s health department even advised people not to kiss “except through a handkerchief,” and wire reports spread the message around the country.

In western states, some cities adopted mask ordinances, and officials argued wearing one was a patriotic duty. In October 1918, the San Francisco Chronicle ran a public service announcement telling readers that “The man or woman or child who will not wear a mask now is a dangerous slacker”—a reference to the type of World War I “slacker” who didn’t help the war effort. One sign in California threatened, “Wear a Mask or Go to Jail.”

The PSA in the Chronicle appeared on October 22, just over a week before San Francisco had scheduled its mask ordinance to begin on November 1. It was signed by the mayor, the city’s board of health, the American Red Cross and several other departments and organizations, and it was very clear about its message: “Wear a Mask and Save Your Life!”

For the most part, San Franciscans listened.

“Red Cross headquarters in San Francisco made 5,000 masks available to the public at 11:00 A.M., October 22. By noon it had none,” wrote the late historian Alfred W. Crosby in America's Forgotten Pandemic: The Influenza of 1918. “By noon the next day Red Cross headquarters had dispensed 40,000 masks. By the twenty-sixth 100,000 had been distributed in the city… In addition, San Franciscans were making thousands for themselves.”

Newspapers printed instructions for how people could make their own masks at home. People who didn’t comply might face prison time, fines or having their name published in the paper, revealing they were a “mask slacker.”

Crosby writes that flu cases in San Francisco declined in early November. Residents continued to wear their masks through the November 5 midterm elections. After armistice on November 11, San Francisco ended its mask order. A spike in January 1919 led the city to implement a second masking order, but this one faced more resistance.

Around the same time the San Francisco Chronicle ran its mask PSAs, newspapers around the country published a cartoon of a man hacking in public that warned, “Coughs and Sneezes Spread Diseases: As Dangerous As Poison Gas Shells”—again linking fighting the flu to fighting World War I. Newspapers used the cartoon to illustrate coverage of a special bulletin from Surgeon General Rupert Blue about the flu and how Americans could protect themselves from it.

“The value of fresh air through open windows cannot be over emphasized,” Blue said. “When crowding is unavoidable, as in street cars, care should be taken to keep the face so turned as not to inhale directly the air breathed out by another person. It is especially important to beware of the person who coughs or sneezes without covering his mouth and nose.”

Many newspaper carried large-print PSAs with similar advice. One announcement featuring a large picture of a masked woman urged, with unusual phrasing, “Do not take any person’s breath.” In Cincinnati, a board of health sign posted on streetcars told everyone to “Keep Your Bedroom Windows Open!” Like many other PSAs, the sign emphasized that precautions against the flu could also prevent the spread of other deadly infectious diseases like pneumonia and tuberculosis.

Messaging in 1918 also emphasized that special health measures weren’t just important because they kept the person who followed them safe. They were also important because they helped protect those around them. Cartoonist Clifford T. Berryman highlighted this in an illustration of a sneezing little boy and an older man who stood in for “The Public.” Looking at the little boy, the man said: “Use the handkerchief and do your bit to protect me.”