What Happened to the Plague?

Wolfgang - ClinicaYou must not let your doctor watch silly films over the Christmas period, he might get weird ideas; which I got, after watching the last part of this ineffably boring and glossy film ‘The Physician.’  But considering the Ebola hype, what really happened to the plague? The only disease mankind has been able to eradicate is smallpox, although the virus is still being stored in high security laboratories – in case one needs it! And indeed the plague is still around and it is a good example how new diseases evolve – without prior notice.

The first historically verified plague epidemic also reached Europe and appeared suddenly in 541 A.D. It killed an estimated 100 million people all over the world. Europe did not see another epidemic for 800 years until 1345 A.D. and the last major outbreak with 60.000 deaths was in China in 1910. How is it possible that initially 800 years passed quietly? Only because the disease survived in animals only occasionally infecting humans. (There are still cases of plague in the USA every year.) Favorable conditions can lead to an enormous multiplication of the infectious agent and its mode of transmission, thus causing a cluster of cases, which then has the potential of infecting many more until the transmission collapses suddenly, because of its intrinsic unsustainability, exactly like every pyramid scheme does.

The cause of the plague is a bacteria called Yersinia pestis, which lives in some types of rat fleas, but also a multitude of other small mammals. The infection occurs through a direct bite by the flea, through sick animals, through touching an infected source or via droplet infection from other humans. This bacteria is supposed to have evolved suddenly in Mongolia between 1.500 and 20.000 years ago from its twin, Yersinia pseudotuberculosis, which usually causes TB-like illness in animals.

Human infection is mainly food borne, very rare and resembles appendicitis. The genetic information of their chromosomes is identical, the only difference supposedly are the presence of two plasmids in Yersinia pestis.  You may remember in my last article I explained that the chromosome in bacteria is floating freely, compared with the already more evolved single cell organisms, which already are equipped with a nucleous, a command center so to speak. The chromosomes contain the genetic information of a cell and are therefore fairly large.

Plasmids are an additional bonus, containing isolated bits of independent genetic information, which gives the bacteria an advantage over its mates. Interestingly those plasmids can be passed on to other bacteria even to completely different ones. This way one of the Yersinia pseudotuberculosis bacteria suddenly changed into a monster bug. The most famous examples of plasmids are the resistance to antibiotics and the ability to produce genetically engineered insulin.In the case of Yersinia pestis it led to the production of toxins, causing severe illness and death in humans.

The good news is that although in half of the world including Eastern Turkey, Syria, Iraq, Libya and Algeria, plague bacteria are still present in wild animals, Europe is free from them. However not only humans migrate but also animals. As a bacterial disease it responds to antibiotics, on the other hand it is also classified as a biological weapon. After all, the best defense remains a functioning health system and modern sanitation, which we should not take for granted.

 

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