Posted by Danwei on Thursday, November 4, 2010 at 12:41 PM
Recent research points to China as the origin of Europe's medieval bubonic plagues. Malcolm Moore and Gao Hang reviewed the research and spoke to Dr Yu Dongzheng, director of animal to human infectious diseases at the National Centre for Disease Control about the plague in China.
On Sunday, a team of scientists published a paper suggesting that the plagues that ravaged Europe, Africa and the United States in the 6th, 14th and 19th centuries originated in China.
Writing in the Nature Genetics journal, the team (which included Chinese scientists) assembled a "family tree" of Yersinia Pestis, the bacterium which has now been shown to be responsible for bubonic and pneumonic plague, which is usually carried by rats.
The scientists compared the genetic structure of 282 strains of the bacterium, isolated from locations around the world, including China, the US, India, and the former Soviet Union. They looked at how the different strains had mutated over time, and then mapped those timelines against the historical records of plague outbreaks.
The plague of Justinian (named after the Byzantine emperor ruling at the time) broke out in Constantinople in the 6th century after apparently arriving on grain boats from Egypt. The Black Death, which broke out in 1346, may have killed a third of Europe's population. A third pandemic, which broke out in Yunnan in 1855, killed more than 12 million people in India and China alone.
All three pandemics had a common ancestor, a strain of Y. Pestis that evolved in China between 2,603 years and 28,646 years ago (it's difficult to be exact on the timing, and the scientists said they had given themselves a cautious range of dates).
"What we know is that the bacterium evolved in China, and has been in China all this time, and seems most likely to have come out from China," said Mark Achtman, the professor at University College Cork who led the team.
The team also speculates that Zheng He, the 14th century Chinese admiral, may have taken the plague to East Africa in the rats that lived aboard his treasure ships. The scientists mapped the stopping points on Zheng's voyages and compared them to known plague outbreaks in those areas.
Dr Mark Achtman discusses the findings of his team's plague history research
Dr Achtman said he owns a plague handbook, published in China in the 1930s, which contains details of "massive" outbreaks of plague in China at roughly the same time as the Black Death was devastating Europe.
However, inside China there are few existing records of plague outbreaks and specialists said the history of plague is foggy. What we do know is that plague remains endemic in China, in large parts of central Asia, in Africa and the USA. At the end of September there was an outbreak of pneumonic plague in Tibet.
We spoke to Yu Dongzheng, the director of animal to human infectious diseases at the National Centre for Disease Control in Beijing:
"For the past five years, we have had under ten reports of bubonic plague infecting humans in China. In 2004, there were 13 reports in Qinghai and ten years ago we were dealing with ten outbreaks each year, mostly in Yunnan.
"China has the largest bubonic plague prevention network in the world. Over 400 counties monitor the transmission of plague among animals and we have not had a major outbreak of plague since 1956, thanks to this system.
"China tried to eradicate bubonic plague entirely in the 1960s and 1970s, but failed because of our underdeveloped economy.
"However, although modern medicine can reduce the number of cases, the fact that there was a major outbreak of plague in India in 1994 suggests that there is a chance we could be hit with an epidemic, even today.
"At present, we are able to spot bubonic plague cases quickly, isolate them and treat them with antibiotics, which reduces the chances of human to human transmission. But as the climate and the environment changes, the areas in which plague occurs could also change. If the plague spreads to regions where doctors and local medical facilities are unprepared, it could cause serious damage, like SARS.
"In general, bubonic plague does not pass from humans to humans. It has a much longer history than mankind does. Humans become infected through the contact with a set of rodents - and we have 12 plague-carrying species in China. Australia, for example, is plague-free because none of these species live there.
"China has a vast countryside, especially in the west, where these animals are abundant. As a result, plague is currently most concentrated in Gansu, Qinghai, Inner Mongolia, Yunnan and Tibet. People in those areas also risk infection through hunting marmots for their pelts. In the future, we may perhaps be able to reduce the hazard further by farming marmots and develop more stringent oversight on contact with rodents.
"The first recorded outbreak of bubonic plague in China was in 1772, in Yunnan, where tens or even hundreds of thousands of people died. More recently, we had outbreaks in 1910 and 1920, when the plague began in the North East and then spread throughout almost half the country, causing over 100,000 deaths. In 1947, in the Inner Mongolian cities of Chi Feng and Tong Liao, it struck again. Tong Liao was basically wiped out - there were not enough people left alive to bury the dead. We have no records, but there may have also been a Song dynasty plague in Shanxi.
"The current genetic study still cannot accurately trace back and confirm with 100 per cent certainty the origins of the plague. The scientists can only compare which bubonic plague bacteria are closely related, not which one came first. I can only say it is very likely that China also lost millions of lives in the three waves of plague that struck elsewhere, given our population, but I can't confirm it, at least for now.
"We are not who we were in the 1950s, when we thought that it would be a loss of face to admit that plague existed in China."
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