Beijing (AFP) - A Chinese town has been sealed off and 151 people placed in quarantine since last week after a man died of bubonic plague, state media said Tuesday.The 30,000 people living in Yumen in the northwestern province of Gansu are not being allowed to leave, and police at roadblocks on its perimeter are telling motorists to find alternative routes, state broadcaster China Central Television (CCTV) said.Other reports said that earlier this month the 38-year-old victim had found a dead marmot, a small furry animal which lives on grasslands and is related to the squirrel.He chopped it up to feed his dog but developed a fever the same day. He was taken to hospital after his condition worsened and died last Wednesday."The city has enough rice, flour and oil to supply all its residents for up to one month," CCTV added. "Local residents and those in quarantine are all in stable condition."CCTV said authorities are not allowing anyone to leave, although a previous report by the China Daily newspaper said "four quarantine sectors" had been set up in the city.No further cases had been reported by Tuesday.Plague is categorised as a "Class A infectious disease" in China, a report by the official news agency Xinhua said, "the most serious under China's Law on the Prevention and Treatment of Infectious Diseases".Bubonic plague is a bacterial infection best known for the "Black Death", a virulent epidemic of the disease that killed tens of millions of people in 14th century Europe. A more recent pandemic, the Modern Plague, began in China in the 1860s and reached Hong Kong by 1894, the US Centers for Disease Control (CDC) says on its website."Over the next 20 years, it spread to port cities around the world by rats on steamships," it says. "The pandemic caused approximately 10 million deaths."Primarily an animal illness, it is now extremely rare in humans.Modern antibiotics are effective in treating plague, the CDC says, but without prompt treatment it can cause serious illness or death."Human plague infections continue to occur in the western United States, but significantly more cases occur in parts of Africa and Asia," it adds.Cases occasionally emerge in China. A villager who found a dead marmot and ate it with other residents of Litang in Sichuan province, in the southwest, died of the disease in September 2012, a newspaper run by the health ministry reported.Chinese media have not specified whether the latest victim's dog fell ill.