The word plague has a frightening ring to it. For centuries, plague was one of humanity's most feared diseases. The Black Death of the 14th century killed tens of millions of people, devastating communities throughout Europe and Asia.

Now, in October 2026, plague is once again making headlines in Russia.

A laboratory worker in the Irkutsk region of Siberia died following an illness described as pneumonia of unknown origin. Because she worked at an anti-plague research institute, authorities began investigating the possibility of pneumonic plague. People who had contact with her have been placed under medical observation or quarantine. At this point, however, there is no evidence of sustained human-to-human transmission or a widespread outbreak.

So, should we be thinking about another Black Death?

No. And there is a very important reason why.

Plague is caused by a bacterium, Yersinia pestis. Unlike COVID-19, which is caused by a virus, plague can be treated with antibiotics. Modern medicine has transformed what was once a frequently fatal disease into one that can often be successfully treated—provided treatment begins quickly.

There are three major forms of plague.

Bubonic plague is the most common. It usually results from the bite of a flea infected with Y. pestis. The bacteria travel to the lymph nodes, producing the characteristic painful, swollen lymph nodes called buboes.

Septicaemic plague occurs when the bacteria invade the bloodstream. This can lead to severe infection, organ damage and shock. It may develop from bubonic plague or occur as a primary bloodstream infection.

Pneumonic plague affects the lungs. It is the most dangerous form from a public-health standpoint because infected people can transmit the bacteria through respiratory particles. Without treatment, pneumonic plague can progress extremely rapidly.

And here is perhaps the biggest difference between plague today and plague centuries ago:

We have antibiotics.

Doctors do not have to wait for every laboratory test before beginning treatment when plague is strongly suspected. The CDC recommends starting appropriate antimicrobial therapy promptly because delaying treatment can be dangerous.

That does not mean plague is harmless. It remains a serious and potentially deadly infection. But today's physicians have something physicians during the Black Death did not have: effective antimicrobial treatment, modern laboratories, isolation procedures, contact tracing and public-health surveillance.

COVID-19 taught us how quickly a respiratory virus can spread around the world. Pneumonic plague is different. It can spread from person to person, but transmission generally requires close contact with someone who is already ill, and it does not have the same pattern of worldwide spread as COVID-19.

The lesson from Russia is therefore not that the Black Death has returned.

It is that old diseases can still exist in the modern world—but modern medicine has changed the story.

The plague bacterium has been around for thousands of years.

Our ability to fight it has not.