Plague Disease – History And Treatment

By: Michael Lam, MD, MPH

Disease Description

Rodents helped spread plague disease in the 14th century Plague disease is caused by the bacteria Yersinia pestis. The plague is primarily a disease of rodents and carried by their fleas, which can infect humans. It is a severe disease in people with case fatality rates of 50-60% if left untreated. Plague disease has been responsible for widespread pandemics with high mortality in the pre-antibiotic era. It was known mainly as the “Black Death” during the fourteenth century, causing an estimated 50 million deaths.

The most famous outbreak of plague is known as the “Black Death”, occurring in fourteenth century Medieval Europe. Plague spread by rodents and fleas infesting them spread the disease rapidly among the population of Europe starting in the 1340’s. The epidemic reached its height between the years 1348 and 1350 before beginning to subside. All told, it is estimated this outbreak took the lives of 50 million people.

Plague Disease Outbreaks

Outbreaks off the plague disease have occurred both before and after the Black Death, as far back as the Byzantine era. The Plague of Justinian occurred in the years 541 and 542 killing an estimated 25 million people, with a further 25 million dying to recurrent outbreaks over the next two centuries.

Multiple notable outbreaks of the plague have since occurred in Asia, South America, Africa, and even Hawaii. Greater understanding of the disease as well as the advent of antibiotics in the era of modern medicine have limited the spread and virulence of plague outbreaks, and since the 1990’s they have been confined mostly to Africa.

The most recent data from the WHO indicates in 2013 there were 783 reported cases of the plague and 126 deaths. Countries with the highest endemicity of plague are Madagascar, the Democratic Republic of Congo, and Peru.

There are three main forms of plague in human.

  • Bubonic Plague: This is the result of an insect bite in which the plague bacillus, Yersenia pestis travels through the lymphatic system to the nearest lymph node where it form a swelling. Commonly presents with acute and fulminant onset of non-specific symptoms including fever, malaise, headache, myalgias, nausea, vomiting and abdominal pain. After which the bubo develops. The bubonic form may progress to septicaemic and or pneumonic form.
  • Septicaemic Form: Bacteremia is common in patients with bubonic plague. About a quarter of bubonic plague patients progress to clinical septicaemia. This may produce thrombosis, necrosis, gangrene and DIVC.
  • Pneumonic Plague: This condition is an infection of the lung due to either inhalation (primary pneumonic plague) of the organism or spread to the lung from septicemia. Primary pneumonic plague has an acute and fulminant onset of non-specific symptoms followed within 24 hours by a cough with bloody sputum. The pneumonia progress rapidly resulting in dyspnea, stridor and cyanosis. Without treatment, the disease terminates with respiratory failure and circulatory collapse. Pneumonic plague is highly contagious.

Incubation Period

  • Incubation of bubonic form is 2-10 days.
  • Primary pneumonic is 1-6 days (average 2-4 days)

Laboratory investigations

  • Sputum for gram stain and culture.
  • Lymph node aspiration, blood, or cerebrospinal fluid samples for culture.

Medical Management

Empirical treatment should begin when clinically suspected of pneumonic plague as the disease is almost always fatal if treatment is not initiated within 24 hours of the onset of symptoms.

  • Gentamicin 5mg/kg IM or IV once a day
  • Streptomycin 30mg/kg IM once a day
  • Doxycycline 200mg followed by 100mg bid.
  • Chloramphenicol 25mg/kg IV loading dose followed by 15mg/kg IV qid is required for the treatment of plague meningitis.

Total duration of treatment is 10-14 days


Pneumonic plague diseaseFace to face contact (within 2 meters) of patients with pneumonic plague or persons possibly exposed to a plague aerosol should be given antibiotic prophylaxis.

  • doxycycline 100mg bid orally
  • ciprofloxacine 500mg bid orally
  • tetracycline 250mg qid orally
  • chloramphenicol 25mg/kg qid orally
  • Give chemoprophylaxis for 7 days or the duration of risk of exposure plus 7 days
  • Contact of bubonic plague patients need only be observed for symptoms for a week. If symptoms occur, start treatment antibiotics.
  • No vaccine is currently available for prophylaxis against pneumonic plague.


Suspected pneumonic plague cases require strict isolation with droplet precautions for at least 48 hours of antibiotic therapy or until sputum cultures are negative in confirmed cases.

Case Fatality

  • Untreated bubonic plague is approximately 60%.
  • Untreated pneumonic plague is nearly 100%. Survival is unlikely if treatment is delayed beyond 18 hours of infection.

Plague disease