Given the state of medical knowledge during the 19th century, it seems likely that missionaries could have unwittingly spread disease, as they traveled from area to area. Historically, traveling merchants are today thought to have been a factor in spreading disease around the world, although I’m not sure to what extent that was known historically. It was considered a possibility early in Mormon history, if the following article is any indication. Local residents in Western New York State feared that Mormons might spread smallpox, and that Mormon beliefs might exacerbate the possibility:
Mormonism and the Small-Pox
There having been several cases of small pox in the village of James town, Chautauque county, a committee of citizens was appointed to take measures to prevent its spreading. In their report, the committee state that their efforts to prevent the spread of the disease have been hindered by a sect calling themselves Mormonites, who profess to believe that the disorder will not attack them, neither would they spread it, although they might come into contact with others not protected, even if the small-pox matter covered them. Nothwithstanding their belief one of the Mormons had been seized with the disease, and it was feared that this sect would be the means of scattering the infection through the county.
Rochester N. Y. Daily Advertiser
(as reprinted in The Family Magazine, 15 June 1833)
Perhaps the most unsettling part of this from a public health perspective is the reported belief that missionaries wouldn’t be affected by the disease. Not only would any public health official not believe such a claim (despite its biblical basis), but there would remain a fear that even if not personally affected, missionaries might still transmit disease to others, just as citizens in Jamestown in 1833 apparently feared.
Smallpox (which was declared eradicated in 1979) was transmitted either through the air (within 6 feet of an infected person) or through exposure to objects that had been in or on an infected person (such as clothing or bedding). And if my understanding is correct, those infected were not contagious for the first 12 days — until the first pox appeared. This generally meant that those infected would often know that they had been exposed to an infected person.
Missionaries administering to someone ill with smallpox could, of course, easily be exposed, and their belief that they wouldn’t be infected would lead them to do so. Twelve days later the missionary could then easily be in another town, where he could then infect others.
While plausible, I don’t know of any evidence which might indicate that any Mormon missionary actually spread smallpox. But, in thinking about it, I am sure that at some point missionaries may have spread some disease or other. hope that whatever missionaries may have spread unwittingly wasn’t anything lethal. And I’m glad that today we generally have the sense and knowledge necessary to take precautions with communicable illnesses.