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Bubonic vs. Pneumonic Plague: Symptoms, Causes & Differences

Plague, caused by Yersinia pestis, manifests in distinct clinical forms based on portal of entry and dissemination. Bubonic (flea bite → lymph nodes) and pneumonic (inhalation → lungs) are the two major forms, with vastly different transmission dynamics and mortality.

Bubonic Plague (Most Common, ~80%)

  • Transmission: Infected flea (Xenopsylla cheopis) bite → regurgitation of bacteria into skin. Reservoir: rodents (rats, prairie dogs, squirrels).
  • Incubation: 2–6 days.
  • Symptoms: Sudden fever, chills, headache, myalgia → painful, swollen lymph nodes (buboes) in groin, axilla, or neck. Buboes may suppurate.
  • Progression: Bacteremia → septicemic plague (DIC, multiorgan failure) or secondary pneumonic plague.
  • Mortality (untreated): 50–60%. Treated: <10%.

Pneumonic Plague (Most Lethal, ~3%)

  • Transmission: Respiratory droplets (close contact <2m) from human or animal (cats) with pneumonic plague. Person-to-person spread possible.
  • Incubation: 1–3 days (shorter).
  • Symptoms: Fever, cough (productive, bloody sputum), dyspnea, chest pain, hypoxia, rapid deterioration.
  • Mortality (untreated): ~100%. Treated: <15% if started <24h from symptoms.

Other Forms

  • Septicemic: Bacteremia without buboes; DIC, purpura, shock.
  • Pharyngeal/Meningeal: Rare.

Diagnosis & Treatment

AspectDetails
DiagnosisCulture (blood, bubo aspirate, sputum), PCR, F1 antigen detection, serology. BSL-2/3 lab.
First-line AntibioticsGentamicin, streptomycin, doxycycline, ciprofloxacin, levofloxacin, chloramphenicol. Start empirically if high suspicion.
Duration10–14 days (gentamicin 7–10d).
Post-exposure ProphylaxisDoxycycline or ciprofloxacin × 7 days for close contacts of pneumonic plague.
IsolationDroplet precautions for pneumonic (48h after effective antibiotics). Standard for bubonic.

Public Health

  • Plague is a Category A bioterrorism agent (aerosolizable pneumonic).
  • Rodent surveillance, flea control, public education in endemic areas (SW US, Africa, Asia, South America).
  • Vaccine: none currently licensed.

Early recognition and prompt aminoglycoside/fluoroquinolone therapy are lifesaving. Pneumonic plague demands immediate isolation and contact tracing.

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