In The 1700s,

a contagion suddenly appeared in the United States, 

from the years 1702 to 1800, there were, at the least, 35 breakouts of the dreaded disease in the country, and from the years 1800 to 1879, annual outbreaks occurred. The contagion was known as yellow fever, and nobody knew how the virus spread until the year 1900. In the year 1898, however, the Marine Hospital Service had a hypothesis, the Marine Hospital Service, precursor to the U.S. Public Health Service, hypothesized in 1898 that yellow fever was spread by fomites, or materials such as bedding, clothing and other objects touched by someone with the disease. That led to concern that contaminants could arrive on letters sent in the mail, and so they tried to mitigate the risk by disinfecting the letters, after punching holes in them, use of the paddles followed by fumigation with gasses like sulfur dioxide or formalin was widespread by the late 19th century. The practice proved both reassuring and annoying:

“Your very kind letter—came here—punched as full of holes as your Donax sieve, and smelling of hellfire and brimstone—let a clean letter come from the pure of the Green Mountains and the cursed fools at the fumigating station seize it, punch it so that it is almost illegible, then pump an unbearable stink into it,” General F.E. Spinner, a former U.S. Treasurer, wrote to a Vermont friend in 1887.

the above Smithsonian’s paddle is likely from 1899, when yellow fever was finally on the wane, with just a few mild outbreaks in New Orleans, and the Mississippi cities of Vicksburg, Natchez and Gulfport, the paddle has a drawing of a mosquito on the back side; added some time after 1900 when Major Walter Reed, an Army surgeon, proved that mosquitoes transmitted the virus that caused yellow fever. Handwritten above the mosquito is a peculiar verse: “Bacillus Horribilus/Multi Dentura, (Yellow Fever germ),” which is neither the correct name for the pathogen, nor the correct identification, since it is actually a virus, as Reed showed, more details about this story over at Smithsonian, thank goodness nowadays we have virus checkers for our e-mails!