Lab test results have confirmed a suspected case of bubonic plague in western Mongolia's Khovd province, the country's National Center for Zoonotic Diseases (NCZD) said, Xinhuanet.com reports.
The 25-year-old female patient from the province and 19 people in close contact with her remain isolated.
The center said the woman had eaten marmot meat last week.
While hunting marmots is illegal in Mongolia, many Mongolians regard the rodent as a delicacy and ignore the law.
Since the beginning of this year, the Asian country has reported 22 suspected cases, six of which were confirmed by laboratory tests. Three of the six patients have died.
Seventeen out of all the 21 Mongolian provinces are now at risk of the bubonic plague, the NCZD said, urging the public to avoid eating marmot meat.
According to the World Health Organization, the bubonic plague is a bacterial disease spread by fleas living on wild rodents such as marmots and can kill an adult in less than 24 hours if not treated in time.