Diseases, epidemics and smallpox

Painting: in a room, a doctor in old-fashioned dress vaccinates a young boy in the arm, surrounded by watching adults. — Edward Jenner vaccinating a boy: painting by Eugène-Ernest Hillemacher (1884). Eugène-Ernest Hillemacher; digitisation Wellcome Collection, CC BY 4.0, source

In 1721, an enslaved man explains in Boston how to protect oneself from smallpox. The scholar who listens to him is mocked.

Yet the method divides the observed mortality by nearly six.

Then the historians of medicine write the story, and his name often disappears from it.

Diseases, epidemics, contagion

An infectious disease is caused by a pathogen that enters the body and multiplies there: a bacterium, a virus, a fungus, a parasite. This is what distinguishes it from non-communicable diseases — a cancer, diabetes, a heart disease — which do not pass from one person to another.

These organisms travel by a small number of routes, and knowing them helps in understanding most public health measures:

through the air, in the droplets and fine particles given off when coughing, sneezing or speaking — influenza, tuberculosis, smallpox;
through contaminated water or food — cholera, typhoid;
through contact with a person (including through blood or sexual intercourse), an animal or a soiled object;
through an animal vector that carries the agent without always suffering from it — the mosquito for malaria, the flea for plague.

The word epidemic does not denote a serious disease, but a disease that spreads more than expected in a given population, at a given time. A disease that affects as many people as usual remains at its expected level; if it affects markedly more, it is an epidemic. When the phenomenon reaches several countries or continents, it is called a pandemic. When a disease is permanently present in a region, at a roughly stable level, it is endemic there.¹

Endemic and epidemic are defined by each other, and this is what makes the matter delicate. The endemic level is the expected level; the epidemic is what exceeds it. One must therefore know what is usual before being able to say that things have departed from it — and this is why health surveillance counts the sick even when nothing is happening.

Against all this, medicine has three families of means, and they do not act at the same moment. Preventing infection — hygiene, clean water, vaccination. Treating the infected person — antibiotics against bacteria, antivirals against certain viruses, antiparasitics, antifungals, and supportive care. Breaking the chain of transmission — isolation of the sick, contact tracing, mosquito control.

Several of these means were used before anyone knew what they were fighting. This is the case in the two stories this page tells. In Boston in 1721, people inoculate without knowing anything about viruses. In London in 1854, the handle of a pump is removed without anything being known about bacteria. In both cases, the intuition is right — and takes decades to be accepted.

What he knew

The method is called variolation. It consists, most often, of taking matter from the pustules of a sick person and introducing it under the skin of a healthy person through a slight incision.

Originating in Asia, this technique was already practised in 1700 in Africa, India and the Ottoman Empire.²

Caution: This practice was not without risk. The National Library of Medicine (United States) points out that the person operated on could die from it, and pass the disease on to those around them.³⁴

Onesimus

Around 1707, in Boston, the congregation of the minister Cotton Mather gave him an enslaved African man. Mather called him Onesimus.⁵

Mather asked him whether he had ever had smallpox. His answer, as Mather reports it in a letter:

He answered, both, Yes, and No; and then told me, that he had undergone an Operation, which had given him something of the Small-Pox, and would forever preserve him from it; adding, that it was often used among the Guramantese, and whoever had the Courage to use it, was forever free from the Fear of the Contagion.⁶

Yes, and No. An answer that makes no sense within the framework of thought of the man he is speaking to — and that is exactly what makes it interesting.

Then comes a sentence that changes the nature of the exchange:

He described the Operation to me, and showed me in his Arm the Scar.⁷

Onesimus did not merely tell. He produced evidence. A physical, observable mark that could be checked — and he knew what it demonstrated.

Mather then checked with other African captives in Boston, who confirmed how common this practice was in their regions of origin. He also read reports of similar procedures being used in Turkey.⁸

Meanwhile, in 1717, Lady Mary Wortley Montagu discovered this technique in Constantinople.⁹

The knowledge was there for all to see

The most troubling fact in this case is the following.

Slave traders knew how to recognise these inoculation scars — and they raised the price. A person immune to smallpox was worth more.¹⁰

In other words: the knowledge was visible on the bodies, and its commercial value was acknowledged.

People looked at the scar. They did not listen to the person.

Mather asked the question. That is the only thing he did differently — and it was enough.

The 1721 epidemic

Smallpox struck Boston, a town of about 11,000 inhabitants. More than 6,000 cases were reported — over half the population. 844 deaths were recorded, or about 1 in 7 of those infected.¹¹

Mather tried to persuade the town’s physicians to apply inoculation. Only one agreed: Zabdiel Boylston. He began with his young son and two people he held in slavery, Jack and Moll, then several hundred inhabitants — the sources give from 242 to 287 people inoculated, of whom six died.¹²

The figures

Among those inoculated: about 1 death in 40 (1 in 46 in the count Boylston published in 1726, which includes more inoculees).
Among all those infected in the town: 1 death in 7.
Efficacy ratio: Mortality divided by six to seven.¹³

In 1721, well before the formalisation of the modern experimental method, this intervention offers a numerical comparison between two groups — an imperfect one, since the inoculated had not been chosen at random.

A mortality of 1 in 40 to 1 in 46 (2.2 to 2.5%) remains a high rate. Its efficacy can be judged only in comparison with the rate of about 1 in 7 (nearly 15%) observed among the non-inoculated cases.¹⁴

Why it was rejected

The documents of the time reveal three grounds for opposition, and they do not carry the same weight:

Medical: the fear of creating new outbreaks by inoculating healthy people.
Theological: the idea that intervening amounted to thwarting divine providence.
Racial: the refusal to validate knowledge passed on by an enslaved man.¹⁵

The hostility was not limited to words: Mather’s house was the target of an attempted grenade attack.¹⁶

Little is known of his life. In 1716, he had obtained a partial freedom from Mather, by paying a sum towards the purchase of another slave, and still owed him chores. He was married and had children.¹⁷

The Soho pump: the rest of the story

In London, in the Soho district in 1854, 500 people died of cholera in ten days.¹⁸

Dr John Snow challenged the miasma theory (“bad air”) and put forward the hypothesis of waterborne transmission. He mapped the deaths and found them concentrated around the Broad Street water pump. He obtained the removal of the pump’s handle. The epidemic then stopped — but it was already receding before the removal, and the map that made the investigation famous was published only afterwards. The gesture became a symbol; it probably did not, on its own, end the epidemic.¹⁹

The board of health’s rejection of the theory

The local authorities removed the handle, but rejected Snow’s scientific explanation.

Snow set out his thesis in the expanded edition of his book, published in 1855, without winning the support of the scientific community. It was not until 1884 that Robert Koch isolated the cholera bacillus (Vibrio cholerae) in pure culture; the Italian Filippo Pacini had, however, observed it under the microscope as early as 1854.²⁰

The convergence of sanitary measures

The sanitary reform of the nineteenth century drew on both theories:

Supporters of miasma advocated the treatment of sewage, the ventilation of housing and refuse collection.
Supporters of infectious transmission targeted the contamination of water supplies.

A mistaken theory thus contributed to the implementation of adequate public health measures.

Other measures that took time to convince

In 1847 in Vienna, Ignaz Semmelweis showed that handwashing in a chlorinated solution by medical staff drastically reduced maternal mortality from puerperal fever. His 1861 publication met with clear institutional rejection before being validated later.²¹

What these stories have in common

Acting before understanding: a protective measure can be applied, sometimes under compulsion, without agreement on why it works.
What convinces: figures are not always enough to convince as long as one cannot see what is happening inside the body.
Incomplete ideas: a false or incomplete explanation can still lead to measures that genuinely protect.

Historiographical clarifications

On Edward Jenner: Jenner did not discover the principle of actively induced immunisation. He refined the procedure in 1796 by using cowpox (vaccinia), thereby making the procedure much safer.
On the transmission of knowledge: Cotton Mather names Onesimus and says what he owes him: it was through him that he learned of this practice, and he wrote so as early as 1716.²²

Timeline of eradication

Year	Event
1721	Inoculation in Boston by Zabdiel Boylston following information from Onesimus.
1796	Development of the smallpox vaccine by Edward Jenner from cowpox.
1977	Last natural case of smallpox in the world, in Somalia, in October.
1980	On 8 May, the World Health Assembly officially declared that “the world and all its peoples have won freedom from smallpox”.

Sources for the table²³

Note 1

Epidemic refers to an increase, often sudden, in the number of cases of a disease above what is normally expected

Centers for Disease Control and Prevention, Principles of Epidemiology in Public Health Practice