The Bayannur city health commission confirmed the diagnosis and issued a third-level alert, the second from the bottom in a four-level system. Mongolian health authorities are also investigating a second suspected case involving a 15 year old who developed a fever after coming into contact with a marmot that had been hunted by a dog, China's Global Times tweeted.

"At present, there is a risk of a human plague epidemic spreading in this city. The public should improve its self-protection awareness and ability, and report abnormal health conditions promptly," the local health authority said, according to China Daily.

The bubonic plague caused the Black Death that killed around 50 million people in Africa, Asia and Europe during the 14th century, according to BBC News. But public health experts say it is unlikely to give the new coronavirus a run for its money as a global pandemic.

"Unlike in the 14th Century, we now have an understanding of how this disease is transmitted," Stanford Health Care infectious disease physician Dr. Shanti Kappagoda told Heathline, according to BBC News. "We know how to prevent it. We are also able to treat patients who are infected with effective antibiotics."

Bubonic plague is caused by the Yersinia pestis bacterium which is spread from infected rodents to humans by fleas, according to The New York Times. In Inner Mongolia, the rodents in question are usually marmots, and the health alert put in place by Bayannur health officials warns against eating, hunting or transporting potentially infected animals and urges people to report diseased or dead rodents. The alert will remain in place till the end of the year, according to BBC News.

The plague can come in different forms, according to the Centers for Disease Control and Prevention (CDC): bubonic, septicemic and pneumonic. The latter is consistently fatal if left untreated and can be spread person to person via respiratory droplets, according to The New York Times. The bubonic plague is fatal 30 to 60 percent of the time if not treated. Antibiotics can cure it if administered early.

Symptoms of bubonic plague include swollen lymph nodes, fever, chills and coughing, according to CNN. Pneumonic plague infects the lungs.

The plague in both its forms is an example of how the exploitation of nature and the consumption of wild animals can put humans at risk from deadly pathogens. A 1911 pneumonic plague epidemic in northeast China, which killed around 63,000 people, is believed to have been spread by the trade in marmot fur. Last week, two brothers in Mongolia caught bubonic plague from marmot meat, and a couple in Mongolia died of the plague after eating marmot kidney last May.

Worldwide, the plague infects 1,000 to 2,000 people a year, according to World Health Organization data reported by CNN, though that is likely an underestimate.

An average of seven cases are reported every year in the U.S., according to the CDC.