Russian authorities aren’t saying much about the death of a woman who worked in a lab studying plague. But experts say any risk of contagion would be limited. Is there an outbreak of plague in Russia?

The short answer: We don’t know. The slightly longer answer: A woman who works in a remote Siberian lab that studies plague has died of pneumonia. The lab has been locked down and the Russian authorities aren’t saying much, which has fueled speculation and rumors.

There’s a lot we still don’t know. The Times has gathered all the available information and talked to experts to try to make as much sense of it as possible. (Spoiler alert: Don’t panic.) Who died, and how?

Darya Shipilova, a 28-year-old employee of Irkutsk’s Anti-Plague Research Institute of Siberia and the Far East, seems to have died of a mysterious pneumonia earlier this month. Her death prompted Russian health authorities to quarantine the hospital where she died, along with the institute’s staff and other people who were in contact with her. So far, so unsettling. The plague still exists?

Yes. The plague has been with us a very long time. There are still a few hundred cases every year, mostly in Madagascar and Democratic Republic of the Congo, but also in the United States, Russia and other countries.

Many people know the plague as the “Black Death,” a pandemic that is thought to have killed at least a third of Europe’s population in the 14th century.

Yersinia pestis, the bacteria that causes plague, has infected humans for thousands of years, also circulating among rodents and other small mammals, which serve as long-term reservoirs, and fleas, which spread it.