One of the ways viruses begin to lose their impact is the fact that the human body tends to develop immunities to them once a person has had a virus once. If a person has never been exposed to a particular virus — and most humans have not been to today’s coronavirus — that virus’ effects are often much more deadly.

Such was the case in the 16th, 17th and 18th centuries, when smallpox devastated indigenous people across the Americas, none of whom had ever been exposed to the virus. Smallpox killed millions upon millions of people after Europeans landed on American shores, nearly wiping out entire tribes. It’s estimated there were 15,000-20,000 Wabanaki people living in what is now Maine before Europeans arrived in the mid-16th century. Within 100 years, nearly 80 percent of them had died from smallpox, as well as from typhus and flu.

While indigenous people were disproportionately affected, colonists were also affected by those diseases. Smallpox, influenza and measles outbreaks were a regular part of life in the 18th century. A particularly bad outbreak of smallpox occurred between 1775 and 1782 during the Revolutionary War, affecting all 13 colonies, spreading as far away as what is today California, and killing tens of thousands of people. George Washington became a leading proponent of the then-new practice of inoculating his soldiers with smallpox, thus giving them immunity. A proper smallpox vaccine was not developed until 1798, by British scientist Edward Jenner.

Cholera pandemics

Throughout the 19th century, a series of fast-moving, deadly cholera pandemics swept the globe, killing millions. The bacterial disease, spread mostly by water and food contaminated by human feces, has been stopped in most parts of the world by access to clean water. As late as the 1920s, however, it was a real threat, even after a cholera vaccine was developed in the 1890s. Cholera outbreaks are ongoing in both Haiti and Yemen.

Cholera outbreaks happened in Maine on several occasions between the 1830s and 1850s. One account of an outbreak in Bangor comes from 1832, when a chest of clothing belonging to a sailor who died from cholera in Europe was shipped home to Bangor. The contents of the chest were distributed to family and friends, and all contracted the disease. Another cholera outbreak in Bangor in 1849 killed many members of Bangor’s Irish immigrant community, and a cholera outbreak in Lewiston in 1854 killed 200 people.

The 1918 influenza pandemic