Russia’s consumer protection watchdog has tightened border control measures last week after China reported a fresh case of the deadly and infectious bubonic plague in the country’s north.

The diagnosis of a rural herder in China’s Inner Mongolia region marked the country’s fourth plague case since the start of November, Reuters reported Thursday. Three people from Inner Mongolia were hospitalized for plague last month in two separate cases linked to eating wild animals.

The consumer protection watchdog Rospotrebnadzor said Thursday it “took additional measures” at Chinese border checkpoints to reduce the risk of the plague spreading into Russia.

“Rospotrebnadzor asks Russian citizens to take this into account when planning trips,” the agency said and referred visitors to its website for additional information. 

China reported 26 plague cases and 11 deaths between 2009 and 2018, Reuters reported. Plague cases are not uncommon in China, the news outlet said, but outbreaks have become less frequent.

The bubonic plague, known as “Black Death” in the Middle Ages, is a highly infectious and often fatal disease that is spread mostly by rodents. It also has a deadlier variant called pneumonic plague.

This spring, Mongolia placed its border with Russia under quarantine when a married couple died after eating marmot meat, a case that was believed to be linked to bubonic plague. 

Reuters contributed reporting to this article.