Killer Germs: Pneumonic Plague

In the 1950s and 60s, more than ten institutes and thousands of U.S. and Soviet scientists reportedly worked on biological weapons programs, developing techniques to aerosolize Plague particles - leading directly to the contraction of Pneumonic Plague.(1) In the wrong hands, such techniques pose a potentially serious threat to any population that may fall victim to such an attack. The good news, however, is that Pneumonic Plague has not been reported in the U.S. since 1925.(2)

What is it?

The Plague presents in three forms: Pneumonic, Bubonic and Septicemic. These infections are caused by the bacteria Yersinia Pestis, present primarily in the fleas of rats and other rodents.

The first great Plague pandemic began in Egypt in 451AD. Over the next 4 years, the illness swept around the world. Attributed population losses during that time were between 50-60%. In 1346, the second pandemic outbreak occurred. Known as "the Black Death", within 5 years it ravaged the Middle East, killed more than 13 million people in China and another 20-30 million more throughout Europe. The third pandemic began in 1855 and spread to all inhabited continents, ultimately killing more than 12 million people in India and China alone.(3)

How is it Contracted?

The Plague is normally transmitted from an infected rodent to humans through infected fleas. Given advances in public health, improved living conditions, and groundbreaking medical therapies, future naturally-occuring mass outbreaks are highly improbable and unlikely.

In the case of a bioterrorism-related outbreak, the illness would likely be transmitted through the use of aerosol, causing a Pneumonic Plague pandemic. A 1970 World Health Organization assessment asserted that, in a worst case scenario, the dissemination of 50 kg of Yersinia Pestis in an aerosol cloud over a city of 5 million people would likely result in 150,000 cases of Pneumonic Plague; 80,000-100,000 of which would require hospitalization, and 36,000 of which would be likely expected to die.(4)

Without treatment, fatality rates in cases of Pneumonic Plague are 100%.(5)

Bubonic and Septicemic Plague are not readily transmitted from human to human. Pneumonic Plague, however, is highly contagious and can be easily spread from one person to another through cough droplets.

What are the Symptoms?

Symptoms can start as early as 2 days after exposure(6) and include fever, cough with bloody, thick and/or watery sputum, and x-ray evidence of pneumonia. Laboratory tests and cultures must be conducted in order to ensure a positive diagnosis. Without early intervention and treatment, rapid evolution of the disease can occur 2-4 days after symptom onset and can lead to septic shock with high mortality.

How is it Treated?

There is no vaccine currently available against the Plague; however, antibiotic therapies such as Streptomycin, Tetracycline, Gentamicin and Chloramphenicol can all be effective against diagnosed cases. Such therapy should also be administered prophylactically in cases of face-to-face exposure with an infected person.(7 & 8)

The Plague is a potentially lethal threat, however; currently, there is no reason to assume that a bioterrorist attack using Pneumonic Plague as a weapon is going to occur.

Learn More

To keep informed of the latest updates and information on Plague and other biological agents, please visit the the U.S. Department of State's website at http://www.state.gov/www/global/terrorism.

References:
1, 3 & 4: Johns Hopkins University Center for Civilian Biodefense Studies; http://www.hopkins-biodefense.org/pages/agents/agentplague.html
2 & 5: Neal R. Chamberlain, Ph.D.; http://www.kcom.edu/faculty/chamberlain/Website/lectures/lecture/plague.htm
6: Bioterrorism Information Sheets, San Francisco Bay Association for Professionals in Infection Control and Epidemiology
7: Johns Hopkins University on behalf of its Center for Civilian Biodefense Studies; http://www.hopkins-biodefense.org/pages/agents/agentplague.html
8: JAMA 2000;283:2281-2290