What is pneumonic plague?
Last updated 2026-10-05
Pneumonic plague is the most serious form of plague, an infection caused by the bacterium Yersinia pestis. It infects the lungs, either after bubonic plague spreads to them or when a person inhales infectious droplets.
How it spreads
- Person to person: through respiratory droplets coughed out by an infected person, usually requiring close contact.
- Laboratory exposure: inhaling aerosols from cultures is a known occupational hazard, which is why plague is handled at high biosafety levels.
- Animals: fleas and infected rodents drive most natural plague; pets such as cats can also transmit the pneumonic form.
How dangerous is it?
Untreated, pneumonic plague is almost always fatal, and it can progress within one to three days. Treated with antibiotics within roughly 24 hours of the first symptoms, most patients survive. Incubation is short, typically 1 to 4 days.
Is it like COVID-19?
No. Plague spreads less easily than viruses such as influenza or COVID-19, mainly through close contact with a symptomatic patient, and it responds to common antibiotics. Outbreaks are historically contained by isolation, contact tracing and preventive antibiotics, as in Madagascar in 2017 (209 deaths among 2,417 cases, per WHO).
Treatment and prevention
First-line antibiotics include streptomycin, gentamicin, doxycycline and ciprofloxacin. Close contacts are typically given preventive antibiotics and monitored. There is no widely available vaccine for the general public.
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