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The History of Onesimus: The Black Slave Who Helped Stop Smallpox

Updated: Nov 12, 2022

The Characters:

The above photo is not a real picture of Onesimus. This story happens in the 18th century before photography. There are no photos and few if any drawings of Onesimus the slave so we opted to use this photo as a representation.

Hold onto your butts because this one is about to get a little controversial. This story will take us to the infancy of America, actually to a time before America, to the Puritans. Our story starts with a minister with a distinguished theological pedigree who was both pro-slave and pro-Salem Witch Trials. He nearly became a doctor due to a speech impediment, but eventually overcame this and became a minister like his father. So, with one foot in science, one foot in theology and a mind for words our “semi-hero” became an influencer of his time by writing nearly 400 books and pamphlets. Some of his works influenced the course of the Salem Witch Trials resulting in a number of women being killed, while other writings were based on some science and saved lives. Cotton Mather lies somewhere between evil and good and, like us all, is a product of his time. Today, we will talk about him as more of a hero than a witch hunter. His heroic trait in this case was listening to someone no one else would and using his power as an influencer to try to do good in his little town of Boston.

Cotton Mather was in no way a saint, but neither are many saints for that matter. He had some terrible attributes and was involved in 2 very violent and unethical chapters in American history: slavery and Witch Trials. Mather purchased the true hero of this story and renamed him Onesimus; unfortunately, his real name is lost to history. Now take a deep breath because I’m sure you’re about to get as angry as I did when I read this. Onesimus is a biblical name for a slave meaning “useful”.

Not much is known about Onesimus’ life before or after our story, but one could imagine that being a slave in the 18th century to a puritan minister must have been pretty terrible. Yet, he had the courage and desire to help his fellow man where he could have remained silent.

The Crisis:

In the year is 1721, Boston was a thriving colonial town with 11,000 people. While not the bustling city it is today, it was still crowded, unsanitary and a perfect breeding ground for infectious diseases. So, when some sailors rolled into Boston ‘Habah’ carrying highly contagious smallpox, it was a big deal. The Bostonians quickly quarantine the infected, but who knew how many had been exposed.

Smallpox is caused by the virus Variola major, and Variola minor with the infected developing symptoms such as fever, vomiting, rash, fatigue, and fluid filled blisters that will scab over. 30% of those who contract the disease would die and, if you survived, there’s a pretty good chance you would be disfigured for the rest of your life. Oh yeah and maybe blind, so it was definitely something to panic about.

Child with Smallpox

Onesimus heard of the panic and the fear the townspeople had and thought he could help, remembering a procedure he had received when he was young that saved him from smallpox. He knew Boston would never listen to a black slave, but if he could convince his owner, a distinguished member of white society, maybe they would listen to him. He called for the ear of Cotton and was granted an audience. So, Onesimus told him of the procedure called variolation. Although not known to the Puritans, this process was already in use in other parts of the world. It’s a little gross, so go get a vomit bag. In this procedure, you take some pus from someone who is infected and rub it into the open wound of someone else. PLEASE DO NOT TRY AT HOME! In most individuals this resulted in a mild infection in which the immune system has the time to respond to and develop an immunity against the virus.

An account of Small pox inoculation by Zabdiel Boylston

As Cotton Mathers listened to the story, his scientific mind became intrigued. But wait, what if this treatment didn’t work? Right, he needed to test the story, and so he unethically tested this theory on his slaves. Once he was convinced this was the cure, he went out to tell the community. Considering how medicine was at the time, many people were highly against the idea of rubbing pus on an open wound. Eventually, Zabdiel Boylston, a physician got on board with this idea and inoculated 242 people, resulting in only 6 deaths.

The Aftermath:

The smallpox outbreak of 1721 took 844 lives. Onesimus played a pivotal role in stopping the outbreak and saved lives, having the courage to speak and share his experience in a time where his voice was seldom valued. Fortunately, Mather had the foresight to listen and, if only for a second, valued the words of someone he deemed subordinate to himself.

We can learn so much from each other's experiences and should value all people as equals despite race, ethnicity, or educational background. With a little support and a little respect. everyone has something to offer to the world!

Onesimus was able to “partially purchased” his freedom, whatever that means, and not much more is known. In 1806, Edward Jenner developed a vaccine for smallpox using cowpox which is much safer than variolation. Fortunately for us today, due to the result of widespread vaccination programs, smallpox remains one of only 2 diseases that have been eradicated.

Oh, and for my Bostonians out there, if Boylston sounds familiar, it’s not because of this guy. That street is, however, named after a relative of his, Ward Nicholas Boylston who was a philanthropist.

If you have any thoughts about this topic, or if we missed something please let us know by leaving a comment or sending us an email, we'd love to hear from you!

If you liked this article and would like to read more about important black figures in microbiology, click on the links below.


Adeola, N.-B. et al. This slave curbed the smallpox epidemic in Boston in 1721 with an African technique - Face2Face Africa. Face2Face Africa (2018)

Black History Month: Onesimus Spreads Wisdom That Saves Lives of Bostonians During a Smallpox Epidemic | History of Vaccines.

Blakemore, E. How an African Slave in Boston Helped Save Generations from Smallpox. HISTORY (2019)

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