Plague (Yersinia pestis): what is confirmed and what it means

Key facts

• Plague is a bacterial infection caused by Yersinia pestis — it is treatable with antibiotics.
• It has three main forms: bubonic (most common), septicemic and pneumonic (most severe).
• Only the pneumonic form spreads from person to person, through respiratory droplets in close contact.
• It does not spread over distance through the air, nor through water or casual contact.
• In 2026, a laboratory technician died at the Irkutsk Anti-Plague Institute in Siberia after a probable laboratory exposure. Authorities report no confirmed community outbreak.

Confirmed, reported and unconfirmed

We classify every claim about the 2026 Irkutsk case by its level of confidence, so readers can tell verified facts from press reports and speculation.

In-depth guides

Detailed, source-based content on the clinical forms, transmission, diagnosis, treatment and prevention of plague. Each guide is written by our editorial team and references WHO and CDC material.

• Forms of plagueBubonic plague: symptoms, bubo (swollen lymph node) and treatmentA complete guide to bubonic plague: symptoms, the bubo, transmission by fleas, incubation, diagnosis and antibiotic treatment.~4 min read
• Forms of plaguePneumonic plague: is it contagious? Symptoms, transmission and fatalityPneumonic plague is the most severe form and the only one that spreads between people. Symptoms, transmission, fatality and treatment.~4 min read
• Forms of plagueSepticemic plague: what it is, symptoms and why it is so seriousSepticemic plague: how the bacterium spreads through the blood, symptoms such as shock and bleeding, and why early diagnosis matters.~3 min read
• TransmissionHow plague spreads: fleas, rodents and person-to-person transmissionHow plague is transmitted: the rodent-flea-human cycle, the role of the rat flea and person-to-person spread in the pneumonic form.~3 min read
• SymptomsPlague incubation period: how many days and what to watch forThe incubation period of plague by clinical form, why it matters for contact tracing and what to do after an exposure.~3 min read
• DiagnosisHow plague is diagnosed: tests and differential diagnosisHow plague is diagnosed: clinical suspicion, samples, culture, PCR, F1 antigen testing and differential diagnosis.~3 min read