Microbes in the news: Yersinia pestis (plague)

In the fourteenth century, the Black Death (bubonic plague) spread from China across Europe along trade routes, killing approximately one-third of the population along the way. What’s easy to forget is that the bacterium that caused this massive event is still around – and with it, the plague. This week, we have a sad reminder: the Oregon man recovering from plague who has lost fingers and probably toes to the disease.

Depictions of microbial diseases show up in surprising places – are these plague buboes shown in the St. Louis Cathedral in New Orleans?

What causes the plague?
Plague is caused by the bacterium Yersinia pestis. It normally lives in rodents, and it can be transmitted to other rodents by fleas. People can also be infected if they are bitten by a flea or, more rarely, if they have direct contact with an infected animal. If transmitted via a flea bite, the bacterium travels to the nearest lymph node and replicates, causing a painful, swollen lymph node called a “bubo”. If the bacterium is transmitted directly to the bloodstream, however, disease can occur without bubo formation.

Why is the plague still around?
It’s easy to think of the plague as a thing of the past and, indeed, our improved sanitary conditions mean that few people come into contact with infected rodents (and their fleas) on a regular basis. However, imagine how hard it would be to eradicate an infection from a rodent population world-wide. Impossible? Maybe. At any rate, rodents in several countries, including parts of the US, still carry Y. pestis, and that means we still have a reservoir for the disease.

The good news is that most Y. pestis strains remain sensitive to antibiotics, so the plague is generally a treatable disease. The trick is to catch it early enough, which means that healthcare professionals need to be aware of the risk of plague in their area.

Some resources about the plague:
World Health Organization factsheet
Yersinia pestis genome sequence
MiddleAges.net
Year of Wonders, by Geraldine Brooks, a fictional account of a true story in which a town voluntarily self-quaranteened when the plague hit.

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