Ring a Ring o' Roses: Bubonic plague is much more widespread than you think

It is a disease all British children learn about at school – and one we tend to think of as consigned to the history books.

But the plague – which killed some 50 million people in the 14th century when it was known as the Black Death – is still doing the rounds, as the recent death of two people in Mongolia has brought to the fore.

The pair died from bubonic plague after reportedly hunting and eating marmots – large rodents which can carry the plague-causing bacteria, Yersinia pestis. The case triggered widespread panic and a six-day quarantine in the country's western province, Bayan Olgii.

While hunting the animals is illegal in Mongolia, eating marmot innards is a folk remedy thought – ironically – to bring good health.

According to the country's National Centre for Zoonotic Disease, at least one person dies of the illness every year in the central Asian country, usually after coming into contact with the bacteria-carrying rodents.

“In Mongolia there have been cases reported for well over 100 years, and the plague has probably been there for time immemorial,” said Jimmy Whitworth, professor of international public health at the London School of Tropical Medicine. “It’s perhaps the biggest and most persistent hotspot.

“We think that the Black Death came out of Mongolia originally, and that it was the Mongolian armies expanding westwards that allowed it to spread and get to Europe,” he added.

But the disease is not confined to Mongolia. Between 2010 and 2015, there were 3,248 cases reported around the world, including 584 deaths.

Even the United States reports new cases each year – with 14 fatalities recorded in the country over the same five year period. And in 2015, parts of Yosemite National Park were closed due to an outbreak.

But it is Madagascar that faces the biggest battle against the plague.

The country sees seasonal outbreaks with as many as 600 infections every year, but this escalated in 2017 when an outbreak of pneumonic plague killed more than 200 people before it was contained.

It is thought that the disease spread to the African island from south Asia during a major outbreak in the 19th century which killed some 12 million people in India and Hong Kong.

But large outbreaks like this are unlikely to occur in developed countries – today the plague is a disease of poverty, particularly in Africa and South America. The last case in the UK was just over 100 years ago.

“I don’t think you would be able to really sustain an outbreak in a well developed country,” said Professor Whitworth. “[Plague] doesn’t spread easily from person to person, it means being bitten by fleas – but modern populations don’t really come into contact with fleas.”

Rodents are an ideal host for the disease. While they do die from the plague, they first maintain high levels of the bacteria – allowing them to infect hundreds of fleas who go on to spread the disease.

There are three main forms of the plague but only pneumonic plague, the most deadly, can be spread between people by coughing. This type of the disease is always fatal without treatment - but it can, like other types of plague, be treated with antibiotics if caught early.

Bubonic plague, characterised by painful swollen lymph nodes and fever, is the most common and is fatal in 30 to 60 per cent of cases. The bacteria can also enter the bloodstream, causing septicaemic plague - where the skin can turn black and die, particularly on fingers, toes and the nose.

The centuries old disease – which wiped out a third of Europe 700 years ago – is unlikely to disappear anytime soon, partly because sporadic human infections make it difficult to get a handle on the prevalence of the plague in the wild.

And research published last year suggests the deadly disease could also be lying dormant in common soil and water sources, posing a serious public health risk.

“It’s pretty unfeasible really to eradicate,” said Professor Whitworth. “Getting rid of fleas in the environment is an impossible task.”

Protect yourself and your family by learning more about Global Health Security