A couple diagnosed with pneumonic plague in November are believed to have become infected after the husband was exposed to the bacterium in the air while tilling the soil of his farm, according to a report Friday from the Chinese Center for Disease Control and Prevention.

The two patients — a herdsman and his wife from the northern region of Inner Mongolia — were diagnosed with plague at a Beijing hospital on Nov. 12. According to the report, the husband experienced fever, vomiting, and chest pains, among other symptoms, after working on his farm. His wife became infected after being in close contact with him. The couple were treated with antibiotics at a local hospital before being transferred by ambulance to Beijing.

Two days after the confirmed cases in Beijing, a third individual in Inner Mongolia was diagnosed with the bubonic form of plague at a local hospital. This patient — whose case was not epidemiologically related to the other two — had become infected from skinning and eating a wild hare.

The Mongolian Plateau has seen several cases of rodent-borne diseases this year, the report said. As of Nov. 21, some 447 people in Beijing and 46 in Inner Mongolia had been quarantined over possibly coming into contact with the infected individuals, according to the report. All of them have since been discharged, though the couple who were first diagnosed remain in critical condition.

A fourth case of plague was diagnosed in Inner Mongolia on Nov. 27, though it’s not yet clear how the patient became infected. (Image: VCG)