Officials quarantined part of a city in China after a man died of the bubonic plague last week, the BBC reported.

The 38-year-old patient died in the Gansu province city of Yumen on July 16. Sections of the city's center and three areas of the neighboring town of Chijin have been sealed off, according to state-run news agency Xinhua, the BBC reported.

Officials also quarantined 151 people out of the city of 100,000 who came in contact with the infected man. They are under observation and could be released after nine days if no one becomes sick. So far no one has shown any symptoms, which take up to 10 days to appear, according to the World Health Organization.

The bubonic plague, one of the world's oldest known diseases, wiped out 25 million people across Europe during the Middle Ages. Rodents are the main carriers of the disease, which can spread to humans when handling infected animals. Infection also occurs when humans are bitten by fleas that live on rodents.

Officials believe the victim contracted the bacteria when he fed his dog a squirrel-type rodent called a marmot, the BBC reported. He was admitted to a hospital with an increased heart-rate and appeared to be in shock. The hospital was also sealed off.

The plague, caused by the bacteria Yersinia pestis, is characterized by a bubo, or a swelling of the lymph node where the person was bitten, according to the WHO. Chances of survival are good if the disease is caught early. But if the bacterium reaches the lungs, known as pneumonia plague, the mortality rate is extremely high.

Nowadays the disease is rare. However cases still occur in rural areas. Yumen city saw its last case of the plague in 1977, according to Xinhua news.