Monday, July 28, 2008

Rare Diseases: Yersinia Plague

Yersinia plague is most famously known as The Black Death, a name given to it in the 14th century pandemic that swept away 25 million souls over the course of five horrific years. When plague is mentioned in modern times, folks often scoff - that stuff only happened in the middle ages, right? Nope. Each year, 10-15 cases of Yersinia plague are reported in the United States, and as many as 300,000 deaths world-wide are attributed to the bacteria which causes three distinct forms of plague - bubonic, septicemic, and pneumonic. Asia and Madagascar are currently experiencing "mostly controlled" epidemics, and three major pandemics, the most recent of which began in the 1980's, have brought this deadly menace to nearly every corner of the globe, with the possible exception of Australia.


Yersinia plague is caused by the bacteria Yersinia pestis (see photo). Y. pestis is a rod-shaped bacteria that has developed a solid reservoir among wild rodent populations, including prairie dogs, squirrels, and chipmunks but most famously associated with rats. In fact, it is speculated that the plague originated in Egypt and was introduced to the rest of the world by the black rat stow-aways on trade ships. It is very rare indeed for a human to be infected directly by a rodent, however. Much more commonly, the fleas that pester the infected rats spread the disease among humans. Y. pestis closes off the throat of the fleas, making them unable to swallow food. The poor starving parasites go on a feeding frenzy and with each bite and unsuccessful suck, spread the bacteria into their intended snacks - other rodents, wild animals, and humans.

Bubonic Plague

The most famous form of Yersinia plague, the bubonic plague, is also the least fatal of the three forms. Initial symptoms include the development of large, painful "bubos" (see photo below). The bubos are actually very swollen lymph nodes which served as points of initial infection and most often show up in the groin, under-arm, or neck. They tend to be red with a bruise around them and the tissue may die, turning the characteristic black color. Other symptoms make the common flu look like a kiddy ride - high fever, nausea, vomitting (possibly bloody), severe muscle/joint pain, sore throat, headache, debilitating weakness, chills, and a general sense of feeling so miserable you'd gladly lay down in front of a steam roller for a little relief. With modern antibiotics, if given quickly, the relief is more likely - only 15% of patients treated with antibiotic therapy and supportive therapy die, as opposed to 40-60% of people who go untreated. Bubonic plague can lead to septicemic or pneumonic plague.

Septicemic Plague

Septicemia is a severe, generalized infection - the bacteria circulate through the blood stream and can impact any organ in the body. Septicemic plague can occur after the formation of bubos or without bubos (rare) and the symptoms listed under the bubonic form of the disease. In addition, septicemic plague can cause symptoms throughout the body depending on which areas are affected - diarrhea (often bloody), constipation, severe belly pain, cough (often bloody), muscle pain, stiff neck, bleeding from just about anywhere, gangrene of the fingers, toes, penis, or nose, seizures, confusion, delirium, or coma. Untreated, septicemic plague is 100% fatal and can lead to pneumonic plague.

Pneumonic Plague

Pneumonic plague can be contracted two different ways - from the advancement of bubonic or septicemic plague or from coming into contact with another person or animal who has pneumonic plague. This form of the disease may include bubos and bloody cough, along with general symptoms of the plague and signs of pneumonia. The difference here is unlike bubonic plague and septicemic plague, pneumonic plague is extremely contagious person-to-person. While the other forms of Yersinia plague can pass person-to-person with close contact and exchange of bodily fluid, stepping within a few feet of a person suffering pneumonic plague and taking a few unprotected breaths can be quite literally a death sentence. Survival if treated with modern antibiotics within the first 24 hours of infection with pneumonic plague is often effective at preventing death, but left untreated, this form of the plague is 100% fatal.

The pandemics that swept through the pre-modern world drastically altered the face of the world, not just in terms of the depopulation, but in political, scientific, and religious terms as well. Volumes have been written which point to the Black Death of 14th century Europe as the single most important disease event in shaping the face of the modern world, creating the infancy of modern medicine and ending the dark ages.

Modern sanitation, pest control, and antibiotics have reduced this one-time mega killer to a smaller stature on the scale of world threats, but modern man might yet feel the real bite of this beast. In the age of terrorism, Yersinia plague in aerosol (airborn) form is considered one of the most feared as a potential biological weapon. And unlike small pox and polio, this deadly disease has host colonies the world over and will very likely continue to be a threat looming over us forever.

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2 Comments:

OpenID suelder said...

I heard that Al Kaeda had an outbreak of plague at one of their training camps.

How infectious is plague? Can they spread plague throughout the world through their cells? Or would just the cells be wiped out?

Lot of plotbunnies in there.

January 19, 2009 7:06 PM  
Blogger Arizela said...

This particular kind of plague is already all over the world. It primarily lives in rodent populations and is rarely a human illness these days because of efforts to keep rodent populations down. However, if contracted by humans, and if changed to the airborne form of the disease, it is HIGHLY contagious and HIGHLY deadly. It is also easily cured with modern antibiotics if treated within 24 hours, so while immediate death tolls would be high, as soon as the disease were diagnosed, antibiotic therapy would prevent massive world-wide outbreaks. And I'm honestly not sure if the airborne form of the disease can be manufactured or "bottled" to spread in cellular form.

January 19, 2009 8:15 PM  

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