Disease: Bubonic Plague

Like mosquitoes spread malaria, fleas spread the bubonic plague.  It isn't a coincidence that the plague has evolved very specifically to assure its proliferation (most diseases have, which is why I find them so fascinating).  Check it out: Fleas consume blood, and, like you'd expect, need to bite animals to draw the goods.  Now, if a flea bites a rat infected with the plague, the bacteria moves to the flea.  Not coincidentally, fleas are the perfect host for the bacteria's reproduction.  The bacteria settles in the esophagus and, as it grows, blocks access to the stomach.  That is an amazing example of specific evolution: the blocked stomach keeps nutrition from the flea, and, out of pure hunger, the flea tries to feed from any animal it can (some rats, some human, some dog, etc.) to satiate the hunger... but digestion is impossible.  The flea regurgitates slightly into each of the bites, spreading the plague's bacteria.  Triple ay yay.  The flea, after the fruitless eating frenzy, dies of starvation.

Now, the disease needs fleas to transfer from rats to humans.  (All rodents can be carriers, but rats are the highest source for human contagion.)  In a time when global trade was thriving and agriculture was fruitful, there was plenty excess food in Medieval Europe.  We might as well call that excess food a rat magnet.  And so came the plague. 

The thing is that rats can be affected by the bubonic plague.  Some are unknowing asymptomatic carriers, but others suffer from the plague's effects like humans do.  So, when the rats started showing symptoms (exploding in the streets!), you'd think Europe would have taken notice, but they didn't even know what to look for.  I mean, in the 14th century they didn't even know what viruses or bacteria were.  They didn't even know how reproduction and genetics worked.  Heck, they still believed you could make mice by throwing damp underwear and some wheat in a jar, then returning in 21 days to see a mouse had formed there.  Seriously!  It was called spontaneous generation.  So, rats exploding from bubonic plague was a pointless sign back then, because people didn't even know what signs to read.  It's like putting an alarm clock in front of a caveman.  They wouldn't know better, as the machine blares its wakeup scream.

The bubonic plague's symptoms are really heinous.  (I was searching for photos to include in the article, and they were entirely too disgusting.  I went with a painting that tried to capture Europe's madness from the Second Pandemic.)  It does terrible things to the body, so I'll have to be delicate in how I describe its effects. 

Once someone is bitten, they get a fever, chills, aching joints, nausea.... in other words, it feels like the flu.  More alarmingly, though, buboes appear where there are high concentrations of lymph glands: neck, arm pits and groin.  These buboes are lumps, essentially, made up of swollen lymph nodes (that are fighting the bacteria) and blood from internal bleeding.  The skin turns black from the swelling and internal bleeding.  Eventually, the buboes break, oozing pus and blood.  In addition, the swollen glands drain liquid into the blood stream (as they do even in healthy people), spreading the plague's bacteria around the body where it can sink in some more anchors.  If not treated, the bubonic plague can lead to death within 8 days.

So, is this plague still around?  Yes.  There was a Third Pandemic in China, 19th century.  It is thought to have taken 15 million lives, and it has not been totally irraticated.  Why?  Well, some rats are immune to the effects of the plague, so they are unaffected, ignorant carriers.  Fleas get near them, and humans get near the fleas... well, you know how it goes.  Beyond the Third Pandemic, though, the truth is that the disease is still wherever you find rodents, which means, everywhere in the world: desert, forest, plain, field, city.  Worldwide, there are 1,000-2,000 cases of bubonic plague a year, according to the Center for Disease Control.  Someone who contracts the disease should be treated with antibiotics within 24 hours; That drops the mortality rate down to below 5%. 

The transfer of this disease rings too close to malaria spread by mosquitoes and Lyme disease spread by ticks to humans... but those are other posts.

This Bubonic Plague?  It's some serious stuff.  I'm glad that we know what bacteria is now.  And antibiotics.  I mean, spontaneous generation?  Talk about putting yourself behind the 8-ball!  Keep an eye out for those sick rats!