Pneumonic plague: the form that frightens people.
Bubonic plague spreads by flea bite and rarely passes directly between people. Pneumonic plague is different: it lives in the lungs and rides on a cough. That is the form the world is watching in Siberia.
What is pneumonic plague?
Plague is caused by the bacterium Yersinia pestis and has three main clinical forms: bubonic (lymph nodes), septicaemic (bloodstream) and pneumonic (lungs). Pneumonic plague is the only form that spreads reliably from person to person, through infectious respiratory droplets from a coughing patient. It can also be caught directly by inhaling those droplets, without any flea bite at all.
What are the symptoms?
CDC describes a rapidly worsening lung illness: sudden fever, headache, weakness, then a cough — often with bloody or watery sputum — chest pain and shortness of breath. Illness can progress in hours, not days, which is why a suspected exposure plus new symptoms is treated as urgent.
- Fever, chills, sudden weakness
- Cough, chest pain, breathlessness
- Sputum may be watery or bloody
- Bubonic signs (swollen, tender lymph node) may also appear
Is the plague contagious?
Bubonic plague — the common form — does not ordinarily spread directly between people. Pneumonic plague does: close, face-to-face contact with an untreated, coughing patient is the risk setting. This is why a single pneumonic case in a Siberian research city moves quarantine authorities faster than a hundred flea-bite cases in the steppe.
What is the survival rate?
The WHO puts the bubonic case-fatality ratio at 30–60% untreated, and says pneumonic and septicaemic plague are always fatal when left untreated — historically, treatment must start early to change that. With prompt, appropriate antibiotics, recovery is realistic. Timing, not luck, is the deciding variable.
How is it treated?
Plague is a bacterial illness, and antibiotics work against it — doxycycline, streptomycin and related drugs are standard options, chosen by severity, age and circumstances. CDC advises starting treatment on strong suspicion rather than waiting for laboratory confirmation, because the pneumonic form moves faster than most lab pipelines.
Why does it matter for the 2026 Irkutsk case?
The researcher who died in Irkutsk fell ill after a laboratory incident involving plague bacteria, and she died of pneumonia whose cause Russia had not named. Pneumonic plague is exactly that picture: a fast lung illness after direct exposure. If Russian authorities confirm it publicly, it becomes the first pneumonic cluster the West has watched closely in decades — which is why the WHO wants the raw data.
Common questions
- What is pneumonic plague?
- Pneumonic plague is the lung form of plague, caused by the bacterium Yersinia pestis. It is the most severe form and the only one that spreads reliably between people through respiratory droplets.
- How does pneumonic plague spread?
- Through infectious respiratory droplets — a cough from an untreated patient. It can also be caught directly by breathing in those droplets in close contact, with no flea involved.
- Can pneumonic plague be cured?
- Yes, with antibiotics — but early. Untreated pneumonic plague is essentially always fatal; prompt treatment is the difference between a news story and a tragedy.
- Is the 2026 Irkutsk case confirmed pneumonic plague?
- Not publicly confirmed. The 28-year-old researcher died of pneumonia of unnamed cause after a laboratory exposure to plague bacteria; the WHO says the cause remains undetermined and has asked Russia for data.
This page summarises public-health guidance (CDC, WHO) and the tracker's own dated records. It is general information, not medical advice. See the Russia plague timeline, who Darya Shipilova is and the other health guides.