5 things about the plague

Cars are parked on the square outside Lanzhou railway station in Lanzhou, north-west China's Gansu province, on May 7, 2014. -- PHOTO: AFP
Cars are parked on the square outside Lanzhou railway station in Lanzhou, north-west China's Gansu province, on May 7, 2014. -- PHOTO: AFP
This photograph depicts the colonial morphology displayed by Gram-negative Yersinia pestis bacteria, which was grown on a medium of chocolate agar, for a 72-hour time period, at a temperature of 25 deg C. -- PHOTO: WIKIMEDIA COMMONS

A man dies from bubonic plague. An entire city gets locked down and people are quarantined. Sounds like something straight out of a mediaeval history book.

But it is actually happening in China.

On July 16, a 38-year-old man died from the plague in Yumen in the northwestern province of Gansu. Subsequently, 151 people were quarantined and the city of 30,000 was sealed off with police setting up roadblocks around the perimeter of the city.

Here are five things you should know about the plague.

1. Bubonic plague is caused by the bacterium Yersinia pestis.

Once transmitted to humans, it can take three forms: pneumonic, septicemic and bubonic plagues. According to the Centers for Disease Control and Prevention in the United States, the bacteria circulates in rodent populations.

2. There is a common belief that the bubonic plague is spread by rats.

It is actually spread by fleas that feed on the blood of infected rats and which then go on to feed on humans.

Flea bites are not the only way the disease can be spread. A human coming into contact with fluids and tissues of an infected animal can catch it, as is likely in the case of the man who died in China. Media there reported that he caught the disease from a dead marmot, a large squirrel.

An infected person could also cough out droplets containing the bacteria and another person breathing in the droplets could be infected by pneumonic plague. This method of transmission requires close contact before a healthy person can catch the disease.

3. The first recorded incidence of widespread plague was the Justinian plague in the 6th century.

Named for the Byzantine emperor Justinian I, the pandemic began in 541AD and recurred periodically for the next 200 years, killing an estimated 100 million people in Europe.

There was another outbreak in the 14th century called the Black Death, which began in China in 1334 and spread along the famous Silk Road to Europe where it killed an estimated 60 per cent of the population.

China was again the source of the third pandemic, the Modern Plague, in the 1860s. It spread to Hong Kong and was taken all over the world by rats which travelled on steamships. This pandemic killed about 10 million people.

But this time, scientists figured out how the plague was being spread and in urban areas, pest control meant that rat-associated plague was brought under control.

4. With modern antibiotics and prompt identification of symptoms and treatment, the disease is not fatal.

All plague infections begin with fever, headaches and chills. But patients will then develop other symptoms. Bubonic plague is named for the painful swelling of lymph nodes (also called buboes) experienced by patients.

In the case of septicemic plague, an infected person will suffer bleeding into skin and other organs, and skin and other tissues may turn black and die. Septicemic plague can appear first, or develop from untreated bubonic plague.

Pneumonic plague can develop from both bubonic and septicemic plague after the bacteria spreads to the lungs. It causes the infected person to cough bloody or watery mucous.

5. While associated with historic pandemics, there are still outbreaks of the disease in the modern world.

The World Health Organization tracks outbreaks of the disease and a list of outbreaks since 2001 can be found on its website.

According to WHO, the disease remains endemic "in the tropics and subtropics and in warmer areas of temperate countries". It also notes that "plague may reoccur in areas that have long remained silent".

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