Deadlyblast from the Past; Could the Black Death Strike Again? Plague Still Exists but, as Professor Dave Wagner Tells Lisa Salmon, There's No Need to Panic
Byline: Dave Wagner
MANY people think of the plague as a killer disease that's been safely consigned to the annals of history. However, the truth is that the notorious rodent-borne infection, which killed half the population of Europe during the 14th century's Black Death, still strikes thousands of people every year, and bacteria similar to that which has caused three plague pandemics over the last 1,500 years still lurks in rat populations today.
New research into the pathogen (disease-causing agent) responsible for the first, Justinian, plague pandemic from 541AD, has found that it was caused by a distinct strain of the same pathogen that was responsible for the Black Death.
The findings suggest that a new strain of plague could emerge again in humans.
The disease is usually transmitted through the bites of infected fleas which live on rodents, often rats. "Humans are just an incidental host, but a very important one," explains Dave Wagner, an associate professor in the Center for Microbial Genetics and Genomics at Northern Arizona University, who formed part of an international team of researchers that conducted the new plague study.
They extracted DNA from the 1,500-year-old remains of German victims of the Justinian plague, which is estimated to have killed between 30 and 50 million people - virtually half the world's population at that time.
From the DNA, the team reconstructed the genome (complete set of genetic material) of the plague bacterium Yersinia pestis, and compared it to a database of plague genomes.
"What we found was that the closest relatives to that ancient strain that are still alive today are found in rodent populations in China," says Wagner.
"There was really nothing that drastically separated the first pandemic strain from the strains circulating today."
A bite from a flea infected with one of the strains can lead to bubonic plague, Who, which causes fever, headache, chills, weakness, and swollen, tender and painful lymph nodes called buboes, which progressively darken, giving rise to the name Black Death.
If left untreated, bubonic plague can kill from septic shock within about three to six days of the onset of symptoms, or sometimes turn into the rarer pneumonic plague, which can be spread from person to person through infected droplets, in a similar way to the spread of colds and other respiratory illnesses.
But there's no need to panic - as Wagner points out, if the plague did make a comeback it's unlikely there'd be a pandemic because hygiene has improved and rat populations are controlled.
But the main reason plague isn't likely to decimate humans again is because simple antibiotics, like doxycycline or tetracycline, can stop it in its tracks, if given early enough. Late diagnosis can lead to death, even with antibiotic treatment.
"If it looked like a big plague outbreak was happening, the World Health Organisation and other health bodies would control it with antibiotics," reassures Wagner.
"It's a cautionary tale that there are diseases in animal reservoirs around the world. We have to remain vigilant to them and respond accordingly.
"Humans were involved in the spread of plague in all three pandemics, and we have to take responsibility for that and take care that we're not spreading diseases around the world."
Historically, plague pandemics are thought to have killed at least 100 million people in total, with the first major recorded incidence being the Justinian plague, which helped bring an end to the Roman Empire when it rampaged through Europe for 200 years around the sixth century.
The Black Death struck around 800 years later with similar force, killing 50 million Europeans between 1347 and 1351.
"With the Black Death, there were huge rat populations in places like London," Wagner points out and "It wasn't that long ago that humans, and certainly poor humans, had fleas of their own, so in the bedding there would've been fleas that fed on humans at night. …