Forms of plague
Pneumonic plague: is it contagious? Symptoms, transmission and fatality
Quick answer
- Pneumonic plague is the form that affects the lungs and the only one that can pass from person to person, through respiratory droplets in close contact.
- It is the most severe form: untreated, fatality approaches 100%; even with treatment, delay sharply reduces survival.
- Symptoms include fever, shortness of breath, chest pain, cough — sometimes with blood — and rapid progression to respiratory failure.
- It is the form linked to the 2026 Irkutsk laboratory case in Siberia; authorities say there is no confirmed community outbreak.
What pneumonic plague is
Pneumonic plague is the form in which Yersinia pestis infects the lungs. It can arise in two ways:
- Primary pneumonic plague: when a person inhales contaminated droplets from another patient or, more rarely, laboratory aerosols.
- Secondary pneumonic plague: when the bubonic or septicemic form spreads to the lungs.
It is the most feared form for two reasons: it is the most lethal, and it is the only one that can spread from person to person, potentially causing chains of transmission in closed, crowded settings.
Is pneumonic plague contagious?
Yes. Pneumonic plague is the only form that spreads between people, through respiratory droplets (coughing, sneezing). This requires close, prolonged contact — it does not spread at a distance the way measles or influenza do.
| Route | Occurs? | Detail |
|---|---|---|
| Respiratory droplets | Yes | Close, prolonged contact with a symptomatic person |
| Flea bite | Not directly | Leads to bubonic/septicemic forms, which may progress to pneumonic |
| Airborne over distance | No | Unlike highly transmissible respiratory viruses |
| Casual contact | Not relevant | Sustained proximity is required |
Infectious period
A person with pneumonic plague can transmit while they have respiratory symptoms. After about 48 hours of effective antibiotics, transmission risk drops sharply — which is why isolation is maintained during that initial period.
Symptoms of pneumonic plague
- Fever and chills.
- Headache and profound weakness.
- Shortness of breath that worsens rapidly.
- Chest pain.
- Cough, often dry at first, sometimes with bloody or watery sputum.
- Confusion, bluish discolouration and signs of respiratory failure in severe cases.
The speed of progression is the hallmark: a patient can move from mild symptoms to respiratory failure within days, sometimes less than 48 hours.
Incubation period
Pneumonic plague has a shorter incubation period than the bubonic form: typically 1 to 3 days after exposure. That short window is one reason contact tracing must be very fast.
Fatality rate
Untreated, pneumonic plague is almost always fatal, with fatality approaching 100%. Even with treatment, the prognosis depends heavily on how early it starts: every hour of delay increases the risk.
Time is critical
In pneumonic plague, early antibiotics are decisive for survival. Any suspicion is a medical emergency.
Treatment and isolation
Treatment uses antibiotics effective against Yersinia pestis, started on suspicion without waiting for laboratory confirmation. Options include aminoglycosides (streptomycin, gentamicin), tetracyclines (doxycycline) and fluoroquinolones (ciprofloxacin, levofloxacin), depending on the case.
Patients may also need intensive support: oxygen, blood pressure control and, in severe cases, mechanical ventilation. Respiratory isolation (droplet precautions) is maintained for at least 48 hours of effective treatment.
What about close contacts?
Close contacts of a pneumonic plague case are identified and monitored, and usually receive preventive antibiotics (post-exposure prophylaxis) for several days to interrupt any chains of transmission still in the incubation phase.
The Irkutsk case (2026) and pneumonic plague
The 2026 case at the Irkutsk Anti-Plague Institute in Siberia was described by the media as compatible with pneumonic plague, after a laboratory technician reportedly broke a test tube containing live bacteria. Russian authorities officially described it as pneumonia of unknown cause and said there was no outbreak or confirmed community transmission.
This illustrates a key point: even the most severe form of plague does not, by itself, cause an outbreak — that depends on rapid diagnosis, isolation and contact management.
Frequently asked questions
Does pneumonic plague pass from person to person?
Yes, it is the only form of plague that spreads between people, through respiratory droplets in close, prolonged contact. It does not spread efficiently over distance.
What is the fatality rate of pneumonic plague?
Untreated, it approaches 100%. With early antibiotics the prognosis improves greatly, but delay significantly increases the risk of death.
Is pneumonic plague curable?
Yes, when treated early with appropriate antibiotics. It is a medical emergency, and the time from symptom onset to treatment is decisive.
Is it the same as common pneumonia?
No. Common pneumonia has many other causes. Pneumonic plague is caused specifically by Yersinia pestis and requires specific treatment and public-health measures.
Sources
Medical review
Review by a licensed health professional is being arranged. This educational content is based on reference sources (WHO, CDC and medical literature) and does not replace evaluation, diagnosis or treatment by a health professional.
How this content was produced
- Who
- Produced by the Equipe editorial do Peste.com.br, the editorial team responsible for gathering, verifying and classifying public information about plague (Yersinia pestis).
- How
- Information is compiled from official and scientific sources (WHO, CDC and national health authorities) and from recognised news outlets. Every statement is classified as confirmed, reported or unconfirmed, and each article lists its sources.
- Why
- To offer clear, source-based information in Portuguese about plague and to separate verified fact from rumour. This content is educational and does not replace medical advice.
- Medical review
- Review by a licensed health professional is being arranged; no credential is claimed until a real professional is credited.
- Last review
See our sources and methodology and the editorial team.A revisão por profissional de saúde habilitado está em processo de credenciamento. Assim que concluída, o nome e o registro serão informados nesta página e nos dados estruturados.