THE EXPLAINER
Plague today.
The basics.
Reviewed October 5, 2026
Plague is an infection caused by the bacterium Yersinia pestis. It still occurs today, and prompt antibiotic treatment can save lives.
How does it spread?
People can acquire plague through infected flea bites or contact with infected animals. Pneumonic plague can spread between people through infectious respiratory particles. WHO plague fact sheet.
Three main forms
- Bubonic: infection involving the lymph nodes, often with painful swelling.
- Septicemic: infection involving the bloodstream.
- Pneumonic: infection involving the lungs, which can progress rapidly.
These are clinical forms of the same bacterial infection, not three different viruses. WHO: Types of plague.
Where does plague occur?
Plague persists in animal reservoirs in parts of the world, including the western United States and areas of Africa and Asia. A place with a history of plague is not necessarily experiencing a current human outbreak. CDC: About plague.
Why does early treatment matter?
Antibiotics can cure plague, but treatment must begin quickly to reduce the risk of serious illness or death. Sudden illness after possible exposure needs prompt medical attention. CDC guidance.
It cannot diagnose an infection or assess your personal exposure. For symptoms or a possible exposure, contact a medical professional promptly and follow local public health guidance.
Why the map uses status labels
A media report, a suspected diagnosis, and laboratory confirmation carry different levels of evidence. The map keeps those distinctions visible. Read how we classify reports.