It has long been hard for people to accept that they can be hurt, or even killed, by something they cannot see. But this is exactly what viruses do and have always done; they evade our body’s immune system, hijack our cells to create more viruses, and have consequently caused epidemics throughout human history. More recently, we’ve recognized they can also cause cancers, as well as other changes to our very genomes that we have yet to fully understand the implications of.
Smallpox: Possibly the oldest viral disease on record is smallpox, with accounts dating to 1100 B.C. in China and India. It made its way to Europe around 500 A.D., and then infamously followed the Europeans to the Americas in the early 1500s, destroying Native American populations. Because it is eradicated today, it can be hard to imagine just how difficult life with this disease was; of the people who caught it, up to forty percent died, mainly through damage to their heart, kidneys, or brain. People who survived could still have injured kidneys, disfiguring scars, or blindness (which it was the leading cause of).
Luckily, in the late 1700s, an observant British scientist named Edward Jenner noticed that dairymaids previously infected with “cowpox” (which caused red blisters on cow udders, and is similar to a mild case of smallpox in people) had immunity against smallpox. Using scabs from infected cow udders, Jenner infected several hundred thousand people with cowpox, effectively vaccinating them against smallpox. But even with a vaccine, like many viruses smallpox remained a significant health problem for years; in 1967, ten to fifteen million people were infected, and over two million died. The World Health Organization took action and created an intensive, $300 million program to finally put a stop to the disease, and it worked; it was officially eradicated in 1979.