In May of 1980, the World Health Organization (WHO) pronounced, after two centuries, that the fight against smallpox had ended. This meant that there were no known cases of the disease anywhere on the planet. Many other infectious diseases have returned from the brink of extinction, but few have been so deadly as the only human communicable disease (thus far anyway) to be eradicated.
Most people are familiar with smallpox, if at all, from their history classes or, or films about the conquest of the Americas. But smallpox was not an invention of the Spanish Conquistadors, but something they had naturally grown resistant.
Medical Anthropologists believe that disease began to infect humans starting around the first agricultural settlements of the Old World. Despite such a long history, little evidence exists before 1570 BCE when it appeared in the New Kingdom in Egypt. Many historians believe that the Plague of Athens in 430 BCE and the Antoine Plague that lasted from 165-180 ACE and killed upwards of 7 million people, including the Emperor Marcus Aurelius and hastened the fall of the Roman Empire, were caused by smallpox.
Smallpox made its way to France sometime in the early 700’s. A clergyman writing around the time described the unmistakable symptoms as “a violent fever followed by the appearance of pustules.” He found that if the person lived long enough, the pustules developed scabs, after which the person survived. By the time the disease had reached the rest of Europe, it had spread across Africa and Asia. Smallpox was not a disease of the poor or the aged or the young. It was an equal opportunity killer. And in the Old World, smallpox killed approximately 30% of those who contracted it, while many more were left disfigured or blind. As devastating as smallpox was in the Old World, it was far more destructive in the New World. One significant reason for this great difference was in the immune systems of the two groups.
Helper T-cells are one of the most important cells in that comprise our adaptive immunity, and are a significant part of almost all our adaptive immune responses. Helper T-cells activate cytotoxic T cells that target and kill invading organisms. They also activate B cells that secrete antibodies and macrophages, ingesting and destroying microbes. But a relatively recent discovery is that the American natives possessed a different variant of the Helper T-cell than Europeans. Whereas Europeans maintained an immune response that developed over thousands of years of fighting off bacteria and viruses, the peoples of the Americas had developed an immune system that dealt with the daily concerns of parasitical infection. While their T-cells were better at recognizing invading parasites, combating parasites, they may not recognize many of the organisms the Europeans had adapted to and had brought with them.
The population of the Americas in the pre-Columbian era is estimated to have been between 25 and 60 million people. Of those populations, approximately 95% died as a result of European diseases. At the same time, the Europeans did not have the same kisses as the American natives and were spared the bulk of the infectious disease is of the Americas. With one or two significant exceptions: the reason that the Europeans were immune to so many possible infections in the Americas stems from the fact that Europeans have been caretakers of domesticated animals for several thousand years and had adapted to many common diseases found in domesticated animals that were used for food sources; adapted, but certainly not immune.
The American natives did not possess the same domesticated animals. Cattle, pigs, and horses were absent from the Americas. While the Spanish and Portuguese explorers met with some resistance from natives, the Incas and the Triple Alliance (Aztecs) had largely succumbed to smallpox by the time they arrived. Historians now calculate that the indigenous populations of both American continents were reduced by about 90% from the introduction of smallpox. The Great armies that the conquistadors faced were already greatly weakened by disease. This lesson was not lost on military leaders that would follow (Lord Jeffrey Amherst, the commander-in-chief of British forces in North America during the French and Indian war advocated handing out smallpox affect blankets to his native foes).
This helps explain how a group of fewer than 200 men, over half of which were on foot, manage to defeat an empire, at that time the largest in the world, with a reported standing army of over 70,000.
Today, thanks to the efforts of public health practitioners, medical researchers, and physicians, smallpox is, so far as we know, relegated to a bygone era. In fact, if you were born after 1972, you would not have received a smallpox vaccine. Still, what would happen if smallpox for re-introduced into American society today? The Variola major virus that causes smallpox killed a third of people infected, and was so virulent it claimed the lives of over 300 million people, just in the 20th century alone. Although estimates vary somewhat, the total number of persons killed by smallpox may exceed 2 billion. With an infectious disease so deadly, could ever make a comeback? If smallpox were to make a comeback, there would likely be two possible sources: intentional release, or unintentional release.
The intentional release is the release of the virus by a terrorist or group into a population. The unintentional release is through the thawing of the frozen virus. The residents of a Siberian town lost 40% of its population to smallpox in the 1890’s. The victims had been buried in the upper layers of permafrost along a river, whose banks have begun to erode, due to floodwaters from a warming climate. Russian scientist are concerned that the graves of anthrax-infected cattle can also be found across Russia, including in areas where the ground has thawed two feet deeper than normal. Recently, the thawing of one of the anthrax-killed animals claimed over 100 Reindeer and hospitalized 13 people living in the area. Scientists speculated that the Reindeer were succumbing to the high temperatures, ate the thawed remains of an infected carcass frozen for many years. From there, the infection was passed to the herders.
Regardless of the cause, The Centers for Disease Control and Prevention (CDC)’s Strategic National Stockpile is the nation’s largest supply of life-saving pharmaceuticals for use in a public health emergency severe enough to cause local supplies to run out. The stockpile ensures the right medicines and supplies are available when and where needed to save lives, and this includes, you may be relieved to know, a reported 400 million doses of smallpox vaccine.