A Plague on Both Your Houses – why Plague Still Scares Us

28 July 2014 by Tania Browne, posted in Uncategorized

 

Pretty but deadly - Yersinia Pestis

Credit: NIAID Flickr Library 

When Mercutio spoke of “... a plague on both your houses” in Shakespeare's Romeo and Juliet, he was wishing pretty much the worst thing that was possible at that time. The return of the Black Death, which had killed millions across Europe in the middle of the 14th century, was a very real prospect to a jobbing playwright like Shakespeare in a busy, filthy, rat infested city.

And plague still grips the public imagination today like few other diseases. So when China reportedly quarantined sections of the city of Yumen, following the death of a 38 year old man from bubonic plague on July 16th, the news spread... well, as quickly as the Black Death spread across medieval Europe. But of course, plague hasn't “returned”, it hasn't been hiding anywhere. It never went away.

There are three basic forms of plague all caused by a tricky little bacteria, Yersinia pestis, which is found in animals throughout the world and transmitted to humans through flea bites. Bubonic plague is an infection of the lymph nodes. It's rather like a very bad dose of flu with the added delight of lymph swellings, or buboes, in the groin, neck or armpits. Bubonic plague can't be transmitted between humans, and with modern medicine has an 85% survival rate, so it may seem that the Chinese authorities are making a bit of a fuss, but the worry is what bubonic plague can turn into.

Bubonic plague, if left untreated, can also lead to septicaemic plague which spreads throughout the bloodstream and can cause death even before any symptoms appear. Nasty. Yet still not spreadable from person to person, so your index case is likely to remain just that. The form of plague that you really have to worry about is pneumonic plague, which can also develop from the bubonic form and easily spreads from person to person by coughs and sneezes. Pneumonic plague is the form most likely to create an epidemic, and why an estimated 30 000 Yumen residents are unable to leave the city. And pneumonic plague, without medication, has a 100% death rate.

But of course there are drugs to treat plague, which is why from killing millions before the discovery of antibiotics, between 1 – 3000 cases of plague are reported to the WHO annually (compared to, say, the 207m cases of malaria reported in 2010). Until the late 1990s the antibiotic Streptomycin was commonly used, though almost all countries now use Gentamicin or Doxycycline as the main treatment.

The problem with these drugs for developing countries, is that to be effective they need to be given less than 24 hours after the first symptoms appear. Plague can lead to incredibly fast deterioration, and you can be dead within 24 hours of the first symptoms showing. Not much good when most cases of plague are reported from rural, agricultural communities; often remote areas with a poor infrastructure. The most plague ridden country in the world is currently Madagascar, with 60 deaths in 2012 and an outbreak that caused an estimated 39 deaths in December 2013. It's thought that the breakdown in the country's infrastructure following a coup in 2009 is largely to blame. By comparison, there have been no deaths from plague reported in Europe or Australia since the Second World War, and in the US an average of 7 cases are reported a year (though annual totals fluctuate a fair bit). Many cases of bubonic plague pass from animal to human in the process of skinning animals, so hunters need to be aware of the risks.

While a modern pandemic is extremely unlikely, there have been three plague pandemics that we know of. “The Plague of Justinian” killed around 100 million people across the Roman Empire in 546CE – about half the population – and most likely played a large role in the fall of the empire. Very little is known about this pandemic, and until recently it wasn't even known for sure that the culprit was Yesrinia Pestis, until examining bones found in a German burial pit revealed tell tale DNA. The best know pandemic was, of course, The Black Death that wiped out millions across Europe between 1347 and 1350, but plague swept away millions even at the birth of the twentieth century when plague erupted in the Chinese province of Yunnan in 1855 and rapidly spread via the new speedy steam ships to ports far and wide. Ten years later, 77 ports in 5 continents had been affected. The third pandemic waxed and waned for another 50 years, and 15 million people are estimated to have died during that time.

Because of the traditional “bogeyman” role that plague plays in the public imagination, people have sometimes wondered if it could be used as a biological weapon in the modern age. It's extremely unlikely to be a success for any budding terrorist. During the Second World War the Japanese Army is reported to have dropped plague-infested fleas on centres of population in China and caused some outbreaks, and following the war the US and the Soviet Union both developed ways to aerosolise plague. In 1970 the WHO predicted that 50kg of Y pestis released over a city of 5 million would cause around 36 000 deaths, but if it did it would have to do it quickly – Y pestis is only viable for around an hour outside the body. This also opens up the question of how you would make 50kg of fully operational Y pestis in the first place. Needless to say, so far nobody has succeeded and this has remained a thought experiment for 40 years.

However the situation in China resolves itself, two things are certain; while we might not have seen a case of plague for years in the UK, it's very much a part of life in some other parts of the world. And despite our ability to control it with medicines, Y pestis still keeps its mythical status - the tiny bacterium we all dread.

 


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