Before smallpox was eradicated in 1979, the ebb and flow of the disease had been common in large cities for centuries. By 1775, the American city of Boston had been visited by smallpox epidemics many times in its relatively short history. The disease was treated with dread, but familiarity. What makes the Boston epidemic of the mid-1770s particularly notable was its major distraction, the war which would later be known as the American Revolutionary War. Years later, veterans and patriots would invoke the 'spirit of '76' to recall the days when American patriots were united against a common enemy. Many of Boston's residents may have recalled a much different enemy that year.

Variola

I know that it is more destructive to an army in the natural way than the sword.
— George Washington, in a letter to Patrick Henry, 1777.

First, a word about the disease is necessary¹. Smallpox was one of the deadliest and most unpleasant diseases known to man for centuries. It was a viciously contagious and excruciatingly painful disease which afflicted the human race for millennia. The ordinary form of variola major (the more deadly form of smallpox) takes a predictable course. Infection is followed by a 12-day 'incubation' period without noticeable symptoms. Headaches are one of the first signs of the onset of symptoms. Fever, malaise, backache and nausea occur near the end of the incubation period. The fever then drops, often cruelly deceiving the victims into the belief that they had just fought off a nasty bout of the 'flu. Soon after, though, sores begin to form in the mouth, nose and throat.

Within 24 hours of the first sores appearing, they rupture, and the disease begins to assert itself on the victim's skin. Raised pustules form around the body, often in the very worst places. The bottoms of feet, the palm of the hand, the face, the back and the neck are hard-hit with sores. Sometimes the pustules break apart and emit a foul odour. At this point, some patients experience attacks on the eyes, and are permanently blinded. Two weeks after the symptoms arrive, the pustules begin to scab over, and about a month after infection, the scabs fall off, leaving only some unattractive scars.

Unfortunately, this is the more pleasant form of variola major. Another kind is called hemorrhagic smallpox. It is much less common, but far more deadly – with a fatality rate in the neighbourhood of 100%. Hemorrhagic smallpox results when there is bleeding underneath the skin. The skin becomes dark and rubbery, but no lesions appear. The eyes can turn a red or black colour, like a billiard ball. Blood begins to run from every bodily orifice. The linings of certain organs are dissolved, and parts of them fall out of the rectum, hanging out like a dangling sock. Sometimes the skin begins to come off in sheets.

The death rate for ordinary smallpox can run anywhere from 25-75%, depending on the strain of the disease and the immune systems affected. However, importantly, a single contraction of the disease grants a survivor immunity from its ravages for the rest of their life.

Variolation

COTTON MATHER, You Dog, Dam you, I'l inoculate you with this, with a Pox to you
— A note attached to a bomb at the home of the famous preacher Cotton Mather, a proponent of variolation, 1721.

After generations of death from smallpox, someone discovered that if you take the contagious bits from an infected person (such as the scabs or the pustules) and entered them into the bloodstream of a susceptible person, they would contract the disease; however if a person was deliberately infected in this way, they found that their symptoms were milder and their survival rate much better than those of someone who 'naturally' contracted the disease. This form of inoculation, called 'variolation' became popular in some circles, and feared in others². Variolation had been common in parts of the world for centuries (especially Africa and Asia), but unknown in others. In 18th-century America, it was just gaining recognition, and it was a very controversial thing.

There was some reason to fear the technique of inoculation. Some believed that it only spread the disease further. Inoculees generally did not suffer much, but if they transmitted the disease to someone else, that person would suffer the full effects. Worryingly, many inoculation patients had mild enough symptoms to be able to go about their lives unimpeded. Abigail Adams, the wife of the famous patriot John Adams, wrote that she had, 'attended publick worship constantly, except one day and a half ever since I have been in Town', while she was in the contagious stage following her inoculation in 1776. A medical doctor wrote approvingly that he had barely been affected by his own inoculation, 'not suffering one day's confinement'. The highly contagious nature of the disease (it can be transmitted through contact with an affected person, or it can be airborne) made inoculation a cause for concern. It cannot be doubted that some people would have contracted smallpox because many inoculees lacked precaution.

Some of the colonies in America banned inoculation completely, especially colonies in New England and in the South. The 'middle' colonies of Pennsylvania, New York, New Jersey, Maryland and Connecticut were not as strict in their policies of inoculation. Wealthy New Englanders flocked to the middle colonies to be incoulated. Hower, poorer people could not afford the money and time that inoculation required. As a result, by the time of the American Revolutionary War, a huge number of American colonists were susceptible to smallpox.

Boston

In a world of smallpox, there were two types of people: the immune and the susceptible. One of Boston's leading citizens, the future President John Adams, implied in a letter to a friend that he was only selected to represent his colony at the Continental Congress in the infamously pox-ridden city of Philadelphia because he belonged to the former class, having been inoculated during an outbreak in 1764:

I rejoice at the spread of the Small Pox on another account, having had the Small Pox, was the merit, which originally recommended me to this lofty Station. This merit is now likely to be common enough and I shall stand a chance to be relieved.

This comment would seem to be in outrageously bad taste, but it is quite clear that he is joking, if only because his infamously swollen ego would not have allowed him to make this observation in earnest.

Smallpox had made many appearances in Bostonian history by 1776³, but had been absent in the recent past, causing many of the younger citizens to have no acquired immunity to the disease. Ominously, however, a few cases of the disease began to be reported around Boston in 1774 – Ipswich, Cambridge and Charlestown reported outbreaks of smallpox. The disease flared up as hotly as the patriot tempers of Bostonians – on about the same trajectory, too. After the Battle of Lexington and Concord – the first conflict of what would be the Revolutionary War – there was a fever burning through the whole of Boston.

No Bells

Very sickly : from ten to thirty funerals a day, but no bells allowed to toll.
— From the diary of a citizen of Boston.

'We shall continue the utmost Vigilance against this most dangerous enemy', wrote General Washington to the President of the Continental Congress in 1775. It was during the siege of Boston that these words were written, yet he was not referring to the enemy British across the Charles River. He was writing about the threat of smallpox within his army.

George Washington could walk through the filthy encampments of his ragtag volunteer army surrounding the city of Boston with fear only for his country. It must have been an odd feeling to walk through a throbbing mass of disease without any worry – perhaps like Moses walking on the dry bed of the Red Sea. Washington had lived through an attack of the disease in 1751 while in Barbados and had the scars on his face to prove it. He was therefore immune, but he still had much to fear from the disease; most of his army was vulnerable.

Directly after the Battle of Lexington and Concord, the American Continental Army had begun a siege of the city of Boston. Most of its citizens and a large part of the British army were trapped in Boston because the narrow peninsula connecting Boston to the mainland was cut off by the Americans⁴. The siege would last for almost a year.

Smallpox is a virus, and therefore needs a steady population of uninfected people to thrive. North America itself was an inviting playground for variola. However, the conditions at the occasion of the Boston siege were close to perfect for the variola virus. Few of the American soldiers had been inoculated from variola, partly because they were largely from inoculation-hating New England, and partly because they were poor militia soldiers who wouldn't have been able to afford the procedure if it had been available. Short-term enlistments meant that soldiers came and went frequently, bringing in new bodies for the disease and spreading it to the countryside. Many of the younger soldiers had not experienced a smallpox outbreak during their lifetimes and their immune systems were entirely unfamiliar with the disease. The inherent susceptibility of the Continental Army soldier, along with the terrible conditions of the American encampments, made a smallpox epidemic seem inevitable to General Washington. It was like a tinderbox waiting to catch fire. Looking to resolve the issue, Washington considered inoculating his army, but decided against it, fearing that it would only cause a major outbreak and that the British would take advantage of his army's temporary weakness. He decided on a quarantine, shoving all persons affected by the virus to the nearby cities of Brookline and Cambridge.

Meanwhile, inside the city, the siege prevented about 13,000 residents from leaving – pro-Revolution and pro-British Bostonians alike. As conditions deteriorated over the long months, the smallpox (which had already begun to surface leading up to the siege) reached epidemic proportions. Smallpox thrives where people are hungry or dirty, and Boston was a hungry, dirty city. In July 1775 many of the long-suffering poor Bostonians were allowed to leave the city. However, the Massachusetts House of Representatives ordered: 'Considering the Hazard of propagating the smallpox, the inhabitants of the Town of Boston are to be removed by Water to the Port of Salem'. This action prevented the smallpox-ridden citizens from coming into contact with the American soldiers on their way out of town.

The British themselves were largely unaffected by the Boston epidemic, because almost all of the soldiers had either been exposed to the disease at a younger age or had been inoculated. They had genetic advantages as well, having built up some resistance to the disease over time. Most colonists had no such advantage.

The first snow came on 21 November, and a typically cold winter settled in. Conditions in Boston became even worse. The British had to resort to tearing down old homes for firewood. The disease attacked with renewed force (smallpox tends to thrive during winter months). At around this time, General Howe ordered some of the poor residents of Boston out of the city, apparently to make room for reinforcements. Some suspected that Howe had deliberately ejected these citizens in order to infect the American lines. Washington, while not buying into theories of biological warfare, became almost paranoid. He instituted a strict quarantine and even ordered that letters coming from Boston be dipped into vinegar before they were read. Everyone coming out of the city was subjected to a smoking and cleaning before they could leave. Soldiers who contracted the disease were immediately removed from the lines. Somehow, an epidemic within the army never materialised.

On 17 March, 1776, after nearly a year in Boston, the frustrated British sailed off to Halifax – which was in the midst of a smallpox epidemic itself – leaving Boston for the Americans. Although this was what Washington had been hoping for, he saw the potential for danger before him. The city was still teeming with the disease, and if the army moved in haphazardly, they would surely be infected. He was also fearful that the British had left biological traps behind. 1,000 troops who were immune to the disease were the first to enter the city. Their job was to guard it and prepare it for the rest of the army. Washington tried to stop the flow of citizens into and out of the city, apparently to little avail. Citizens who wanted to see family members, friends or property could not be dissuaded. Frustrated, Washington wrote, 'Notwithstanding all the precaution, which I have endeavoured to use, to restrain and limit the Intercourse between the Town and the Army and Country for a few days, I greatly fear that the Small Pox will be communicated to both.'

In April, General Washington left for New York with his relatively healthy army. They had impressively managed to avoid a full-scaled smallpox outbreak in the ranks. However, Washington did not leave a healthy Boston behind. July 1776 is now remembered as the month when the Continental Congress declared the independence of the American colonies from Britain, but in Boston, the hotbed of revolutionary discontent, it was the month of the epidemic's peak. Red flags hung all over town warning visitors of an infectious household. On 3 July, 1776, the day before the adoption of the Declaration of Independence in Philadelphia, Massachusetts temporarily lifted its long-standing ban on variolation. Boston went crazy with inoculation. One citizen commented that, 'Inoculation became as modish as running away from the Troops of a barbarous George was the last year.' About 5,000 people were inoculated altogether. Around the same time, guards were posted to prevent anyone with smallpox from leaving the city and to prevent anyone with the disease from entering.

The End

By August, the disease had run its course and it began to subside in Boston. By September, the disease was basically gone from the city. Free movement between city and countryside was restored.

The Americans had really been extremely lucky; their army had escaped with little damage and Washington had learned a lesson about the value of inoculation. He would insist that the army use the practice in the future. In a biography of Washington, historian Joseph Ellis wrote, 'When historians debate Washington's most consequential decisions as commander in chief, they are almost always arguing about specific battles. A compelling case can be made that his swift response to the smallpox epidemic and to a policy of inoculation was the most important strategic decision of his military career.'

Increasingly, historians are viewing the American Revolution in light of the diseases which affected it. The years of the American Revolution are the same years of an enormous smallpox epidemic which affected all of North America – from the fur-trading outposts in Canada to the Indian tribes of the Great Plains to the streets of Mexico City – of which Boston was only one small part. The siege of Boston was both the opening salvo of the Revolution and the first major outbreak of the disease in North America. The few hundred who died in Boston were killed many times over as the disease spread throughout the continent. While numbers remain largely guesswork, probably more than 200,000 North Americans lost their lives to this one epidemic⁵. On the eastern side of the continent, smallpox followed the American Revolutionary War throughout, but as the main theatre of combat in the war turned to the south, the tides turned in favour of the colonists. British troops began to encounter a disease that they had no immunity to – yellow fever.