Plague killed an estimated 50 million people in Europe during the Black Death pandemic in the Middle Ages, but modern antibiotics can prevent complications and death if administered quickly enough.

Bubonic plague, which is one of plague's three forms, causes painful, swollen lymph nodes, as well as fever, chills, and coughing.

Mongolia quarantined its region near the Russian border last week after lab tests showed two cases of bubonic plague linked to the consumption of marmot meat, the country's health officials said on July 1.

Mongolia's National Center for Zoonotic Diseases said last week it had identified and tested 146 people who had come into contact with the two infected people.

The center also identified 504 people of secondary contact in the Khovd province.

The Russian Embassy in Mongolia said "there are no grounds for serious concern" as the Mongolian authorities have imposed travel restrictions and isolated infected individuals, according to Russian state-run news agency RIA Novosti.

The embassy also cited Sergei Diorditsu, a World Health Organization (WHO) representative in Mongolia, who reportedly said the province sees seasonal outbreaks of the plague, according to RIA Novosti.

"There are natural foci of plague in Mongolia and the disease is spread by tarbagans [Mongolian marmots]," said the embassy.

"The problem is that local residents who, despite all prohibitions and recommendations of local authorities, continue to hunt them and eat them, as this is a local delicacy."

Authorities in the Chinese region of Inner Mongolia have also confirmed a case of the plague.

The case in the city of Bayannur, northwest of Beijing, was confirmed Tuesday, according to state-run Xinhua news agency.

In 2019 a couple in Mongolia died after eating a raw marmot kidney, triggering a quarantine that left several tourists stranded in the region.

Anywhere from 1,000 to 2,000 people get the plague every year, according to the WHO, but that estimate does not account for unreported cases.