If you’ve ever played Oregon Trail, you know human history is full of terrible diseases.

Thankfully, better hygiene and knowledge of how disease spreads have turned many of these plagues into distant memories. The most famous of them is smallpox, because it was the target of the world’s first vaccine and the first disease to be eradicated.

The last major smallpox outbreak in the United States happened in 1947, where the virus was unleashed on the busy, people-packed streets of New York City. But thanks to some good disease control, only 12 people got sick. Which, considering that millions of people lived in New York, is pretty impressive.

Smallpox is caused by the variola virus and is named for the small, blister-like lesions that form all over an infected person’s skin. Historians believe it originated at least 3000 years ago in northeast Africa and spread across the world through trade, war, and colonization. And wherever it went, it caused fevers, rashes, and death.

It was easily spread through coughing or sneezing up virus-laden fluids, and nearly 30% of those who caught it died. Survivors were often left blind, sterile, and disfigured by horrible pustule scars. In the 20th century alone, estimates say smallpox killed at least 300 million people around the world.

So basically, no one misses you, smallpox. Still, early doctors realized pretty quickly that smallpox survivors were protected against later outbreaks. So as early as 2000 years ago, they developed the practice of variolation, where they intentionally infected people with material from survivors’ pustule scabs to give them immunity.

Usually, that meant either scratching the scab into their arm or crushing and inhaling it. For the most part, that worked, and was much safer than contracting the disease naturally. But it still gave people many of the unpleasant symptoms, and 1-2% of them died.

A breakthrough finally came in 1796 when an English doctor named Edward Jenner developed the smallpox vaccine which was also the first successful vaccine in history. Instead of using smallpox, Jenner’s procedure used material from cattle infected with cowpox, which is another, much milder disease caused by a virus from the small family as smallpox. He found that injecting someone with the cowpox disease made them immune to smallpox, and called this process vaccination, from the Latin word for cow: vacca.

The era of the vaccine had begun. By 1947, thanks to vaccines, smallpox was much less common in Europe and the Americas, but was still widespread elsewhere. Travelers could catch the disease in places that didn’t practice widespread vaccination, and, along with their souvenir T-shirts, bring it home to infect their community.

That’s what happened in New York City. In March, a couple that had been traveling in Mexico returned home, and, shortly afterwards, the husband developed a fever and rash, and was soon hospitalized. Unfortunately, doctors made several incorrect diagnoses, and no one realized the man had smallpox until he died and an autopsy revealed the truth.

At that time, the occasional case of smallpox wasn’t unheard of in the U. S., but this time, others started getting sick. So the city’s health officials urged the entire population to get vaccinated.

But considering almost 8 million people lived in New York at the time, it wasn’t exactly an easy project. Somehow, private labs, military reserves, and city officials were able to supply 1.2 million vaccines within the first 10 days of the outbreak, and people lined up around the block to get them. Before the end of the campaign, at least 2.5 million vaccines were distributed, and this event is considered one of our greatest public health achievements.

During the hype, there were periodic shortages of the vaccine, which caused unrest and set the stage for scammers. One woman even dressed as a nurse and fake-vaccinated 500 people with water so she could impress a suitor. Which is a strange and terrible way to get a date.

Thankfully, most of the shortages and schemes happened after the outbreak was contained. And by the end of it all, only 12 people were infected, and only two died. The disease was primarily contained using ring vaccination, where officials track down and vaccinate anyone who had contact with confirmed patients.

This technique is particularly effective for viruses like smallpox, because by the time someone has enough copies of the virus in their body to become contagious, they’re too sick to move around much. After the New York outbreak, there was only more, smaller outbreak in Texas in 1949, where one person was killed, but it was considered eradicated from the U. S. in 1952.

Then, in the 1960s, the World Health Organization began its global eradication campaign. Since vaccinating every single person would be both expensive and really time-consuming, officials began containing outbreaks with the same ring vaccination technique that stopped the New York outbreak. And after that, it was only a matter of time before the disease became effectively extinct.

The last naturally occurring case of smallpox occurred in Somalia in 1977, when someone traveled with two smallpox patients and caught the disease himself. And the good news is, he made a full recovery and went on to dedicate his life to eradicating polio. The final death from smallpox happened in 1978 after a lab accident, but after that, it was all over.

And just to be safe, all remaining research stocks of the virus are now kept in two restricted locations; one in the United States and one in Russia. Many countries keep vaccines in reserve to protect against any future outbreak, but there hasn’t been one for four decades. And in 2018 the world will celebrate its 40th year with no deaths from smallpox.

Thanks to efforts like the massive vaccination campaign in New York City, we turned what might have been the world’s deadliest plague into a historical footnote, and I think most of us can agree that that’s pretty awesome. And now it's time for an exciting announcement! We know that it can be hard to figure out what to get people for Christmas.

Or to figure out what you want. So, we're trying out a new thing. We've created a store with a limited list of objects that we have in very limited quantity.

These are cool, weird things that will help you learn, experiment on yourself, or display your enthusiasm for your universe. It's called SciShow Finds. And it's a little portal to some artifacts of this universe that we really love!

You're bound to have friends or family who would love these Mars socks, trilobite fossils, or this super nerdy book that changed Hank's life. We'll add new finds...as we find them. And the new ones will replace these ones, so all of these products are only available for a limited time.

And when you buy from SciShow Finds, you're also supporting SciShow, which is awesome! Check it out at SciShowFinds.com.