Few of the monsters created by evolution have been as successful in causing harm to us humans as the Variola virus, responsible for smallpox. Its destruction was so severe and relentless that it was the first time humanity had to take a truly global action against it. It was one of the greatest victories of our species over the natural world, made possible by cows.
Variola is a virus, a tiny machine that only seeks to reproduce itself. Evidence of it has been found in Egyptian mummies and writings from India and China as old as 3000 years. 1300 years ago smallpox killed up to one third of Japan’s population. By the 16th century, it was one of the main causes of death worldwide. In late 18th century Europe, it killed 400,000 people a year. Every third person who went blind did so because of this virus. Even in the 20th century, it still killed at least 300 million people. Smallpox is a relentless monster that keeps coming back, causing death, injury, and disruption to societies.
How could variola be so incredibly deadly for so long and how could we have forgotten its horror so quickly? In 2023, there are only two laboratories left where the living virus is officially stored for research, in Koltsovo, Russia and Atlanta, USA.
Let’s say, through an unfortunate series of events, the virus got out and you got infected. What would happen to you?
How Smallpox Kills: Variola is highly infectious and catches a ride in small droplets you breathe in. Immediately it begins to infect the cells that line your throat and starts killing them, to trick your body into giving it a lift. Whenever cells in your body die a violent death, your immune cells immediately stream to the site of infection to help out. In this case, that backfires horribly. As immune cells begin cleaning up dead cells, eating viruses, and killing infected cells, variola infects a crucial cell of your immune system: your dendritic cells, intelligence cells that gather information and leave the battlefield to get help.
They enter your lymphatic system, a highway network that spans your entire body and connects hundreds of immune bases. In these bases, your heavy defenses are activated and should be the last place an enemy would want to invade, but Variola wants to get here. For about 12 days, the virus quietly infects civilian and immune cells, jumping from cell to cell infecting more and more of them. At some point, a critical threshold is reached and variola starts its attack for real. Millions of viruses use the lymphatic highway to spill into your blood and organs, infecting your whole body. Suddenly, variola is everywhere.
But despite this global attack, your adaptive immune system is struggling to wake up. Your immune cells look for and use critical transmitters called interferons to mobilize the body against viruses. Interferons, as the name suggests, interfere, significantly slowing down virus infections but also quickly activating millions of anti-virus weapons. But Variola is able to deactivate interferons, which stuns the anti-virus side of your defense system. Other systems would usually help, like the complement system, a sort of mobile minefield that can destroy viruses, but Variola also manages to shut this down too.
And so, with little resistance, variola spreads everywhere and infects billions of your cells all over your body. Among the infected are your capillaries, the smallest blood vessels in your body, which die in great numbers. All this death activates an immune cell that you really don’t need right now but that is attracted by death: the Neutrophil. Normally an efficient killer of invaders, great and small, it is not very effective against smallpox. And even worse, Neutrophils fight by vomiting deadly chemicals, which kills even more of your cells. By 1977, the last naturally occurring case of smallpox was reported.
For thousands of years, smallpox was one of the worst diseases humanity had ever known, causing death and destruction, leaving traumatized and maimed survivors in its wake. To combat the virus, people resorted to a dangerous practice known as variolation, where scabs from an infected person were dried out and ground into a fine powder, then blown up the nostril of a patient or scratched into their skin. This method worked because it introduced the variola virus in a part of the body it was not prepared for. However, 2-3% of patients still died from the smallpox or other diseases resulting from the treatment.
In the 18th century, scientists realized that it was not necessary to use the real smallpox virus for inoculation, but much safer to use material from cowpox, a virus that only caused mild symptoms. This led to one of humanity’s most outstanding achievements - vaccinations.
In 1966, the World Health Organization launched a global effort to tackle local outbreaks of the virus, providing vaccines to even the most remote places on Earth. By 1977, the last naturally occurring case of smallpox was reported, marking a major victory for humanity. Smallpox is a virus that only infects humans, so if we could break the chain of human transmission, we could starve it out. In 1980, after nearly 200 years since the first vaccine was used, Smallpox was declared eradicated, meaning no more children, mothers, brothers, uncles or cousins would be killed by it. This was an incredible victory for humanity, as we were able to defeat one of the most dangerous and cruel monsters that had been hunting us for millennia.
Today, we live in an enlightened time where none of us alive today are haunted by the specter of Smallpox. This light is not natural, it was set in the sky by the sheer will of humankind wanting to be safe from the monsters that haunt us. However, because we live without them, we can forget that they ever existed and that they are real, that the diseases might reawaken, or that new ones might be brewing in jungles, wet markets or laboratories, ready to strike us once more. We forget what an incredible gift vaccines are and how hard we had to battle to get them.
We are still protected by the light, but it is cooling each and every day, and we owe it to those who will come after us to make sure it doesn’t go out. We killed one monster and we can do it again.
If you want to continue learning about the fascinating world of biology, Kurzgesagt has you covered with their Human Cell Poster. This poster was researched and designed in collaboration with molecular biologist James Gurney and contains all the latest cutting edge science about organelles, their function and their place in the cellular world. It is expert-approved and designed to be easy to understand and even easier on the eyes. Get the poster now exclusively on the Kurzgesagt shop and support their vision of sparking curiosity.