We may not see ads like these, but the 24-7 rhetoric on the "screaming head" shows & radio freakshows is actually more dangerous..
http://www.assumption.edu/users/McClymer/his394/contagion.html At left is one of a series of ads the J. Walter Thompson agency created for Lifebuoy soap in the 1920s. (For a larger version, click on the image.) Crowds are always dangerous, the copy proclaimed, because there were "almost certainly" carriers of various dread diseases in every crowd. "How many 'Typhoid Marys' are there in this crowd?" the copy asked. Carriers, the ad explained, were perfectly healthy people who had had mild cases of some disease and who "carried" millions of the germs even though they themselves were immune. The most likely "carrier," the ad suggested by placing him in the center foreground, is the one working-class figure in the crowd. Everyone else is visibly clean. But his hat is soiled; he is not cleanshaven.
"Typhoid Mary" was the nickname of an Irish cook, Mary Mallon, who had infected several families who employed her. She was placed in quarantine for three years but released in 1910 on her promise not to seek employment as a cook. Mallon failed to keep her promise. Instead she found a job at a maternity hospital as a cook. There she infected another twenty-five people, two of whom died. Assuming various names, but always working as a cook, Mallon was arrested again in 1919. At the time of the ad, she was once again in quarantine where she would remain until her death in 1938. (Click here to read an account of her career as a "carrier" in The Military Surgeon by the doctor who first uncovered her role in the typhoid outbreaks.)
Contagious disease held special terrors for people in the early 1920s. The great influenza pandemic of 1918-19 claimed over 21 million lives, more than twice as many as died in the "Great War." More than 450,000 died in the United States. 115,000 Americans had died in combat. Yet, one of the public health lessons of the influenza outbreak was that washing with soap provided no protection whatsoever. It was a lesson the J. Walter Thompson agency either never learned or deliberately ignored. Instead it played upon common fears and then promised an illusory protection. What was true of influenza also held for typhoid fever. "Typhoid Mary" had infected so many because she did not wash properly. But those she infected could not have protected themselves by washing. The germs were in their food.
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One answer is the influence of the eugenics movement. At state fairs across the country throughout the 1920s the Eugenics Society of the United States sponsored "Fitter Family" contests. These attracted thousands of contestants who answered questions about their physical and mental health, their churchgoing or lack thereof, their hobbies and amusements, and other matters. Their responses were scored; families with a grade of B+ or higher received a medal bearing the legend "Yea, I have a goodly heritage." The family with the highest score were pronounced the "fittest" average or large family. The pictures below come from the Eugenics Archive project of the Cold Spring Harbor Laboratory and show winners from the Kansas State Fair (top two), the Eastern States Exposition in Massachusetts, and the Texas State Fair.