The Black Death seemed a particularly horrible kind of plague: it would periodically appear and disappear over three centuries. No one could know when an outbreak was really and truly over. After 300 years of uncertainty, no one dared get their hopes up that an outbreak might be the last.

Burying plague victims (Image: Pierart dou Tielt (fl. 1340-1360)/Public domain)

The Third Pandemic, and Beyond

The Black Death struck the world in three separate pandemics—the Plague of Justinian, the Black Death, and the outbreak in India and China at the end of the 19th century. But the Third Pandemic has never been officially declared over. There was even an additional plague epidemic in Surat, India, in 1994, which eerily recalls many aspects of the Second Pandemic from the mid-14th century.

The way the plague began—with an earthquake—was similar to how many of medieval plague accounts describe events. Because the earthquake was mentioned right after the conjunction of planets and before infected air/miasma was released, historically there has been a tendency to discount an earthquake as relevant to the outbreak of the Black Death.

This is a transcript from the video series The Black Death: The World’s Most Devastating Plague. Watch it now, on The Great Courses Plus.

Rats carry fleas that transmit the plague. (Image: Irina Kozorog/Shutterstock)

In 1994, an earthquake near the village of Mamla displaced large colonies of rats from their native territories. As they moved into areas with high concentrations of people, the plague made a jump to the human population. It wasn’t caught quickly because India, like many other countries, had stopped paying attention to or worrying about the plague. Once the infection was established, it followed the movements of people—in this case, migrant workers who were heading into the city of Surat, which had a population of one-and-a-half million.

One factor most likely allowed the plague to gain a strong foothold in the city before anyone understood what was happening was the form of plague the epidemic took. It was not bubonic, with its telltale swelling and petechiae on the skin, nor septicemic, which can kill quickly and is harder to transmit from person to person.

The form that swept through Surat was pneumonic, which in its earliest stages looks very similar to the flu. It’s only when many people suddenly begin coughing up blood that someone might figure out that this is not simple influenza.

Add to this the fact that the first infections raged through the slums of the city, where quarters were close, good health care nonexistent, and governmental oversight severely lacking, and we can see how the plague grew to a tipping point where it could not be effectively contained anymore. It’s estimated that 78% of confirmed cases of plague—not just suspected—were in the slums of Surat.

Learn more about the three predominant varieties of plague

It Was Too Late To Help The Sick

In a chilling turn, the rest of the story follows the familiar template for plague reaction that was seen in the medieval world. Once health care officials did figure out what was going on and tried to react, they found they were woefully underprepared. There was a shortage of antibiotics and medical professionals in the hardest hit areas abandoned their posts.

Yersinia pestis bacteria can infect humans via the Oriental rat flea. It is better known as the bubonic plague. (Image: MichaelTaylo/Shutterstock)

Shortly after the outbreak in Surat, the plague was discovered in Madagascar. Alarmingly, one of the strains of Yersinia pestis found there is resistant to all known antibiotics used to treat plague. It turns out Yersinia pestis is a clever little bacterium, and when it comes in contact with other bacteria, it borrows material from them and rewrites its own genetic code. This process is called lateral gene transfer, and scientists have figured out that Yersinia pestis has recently borrowed from E. coli and salmonella. The lesson here is a chilling one, and it’s one we would all do well to heed.

Learn more about the state of medieval society on the eve of the plague

Epidemic On The Move

There’s always the possibility of bacterial mutation. The Black Death may still be around in part because after its initial virulent outbreak it mutated to become less deadly. After all, a pathogen that kills off most of the hosts it needs to survive is also threatening its own existence. While Yersinia pestis today is arguably less lethal than it was in the 14th century, another mutation and transformation is always possible, and that mutation could go the other direction.

Adding to this concern is the simple fact that the world is much more interconnected today than it was in 1348. If the plague spread so quickly via sea travel and the movement of Genoese merchant ships through the Mediterranean, imagine what an infected person on an international flight might do. We don’t have to imagine it—we know. Both the SARS and MERS epidemics spread quite quickly via international flights.

The important lessons of the Black Death and other plagues are about the people and communities who survived these illnesses. The voices of those people are lost to posterity and the losses were enormous. Many were buried in mass graves or dumped into rivers with nothing to mark their final resting places. But, by and large, civilization remained. It had changed and adapted—but in our world today, which arose out of the medieval world, we are more like the people of the Middle Ages than we are different. This bodes well for the future of humanity, no matter what should come our way.

Learn more about how the plague traveled by sea across the Mediterranean

Common Questions About the Black Death

This article was updated on June 17, 2020