Inner Mongolia autonomous region confirmed a new bubonic plague case Wednesday, local health authorities said late Wednesday night, the fourth such case in China this month.

A herder was diagnosed with the disease when treated in a local hospital in Siziwang Banner in North China's Inner Mongolia Autonomous Region, and had once been active in places that sources of plague were discovered, according to a statement released by the Inner Mongolia Health Commission.

The patient is now being quarantined and is in stable condition after treatment at the hospital. Four other people who had close contact with him have also been put into quarantine for medical observation. None had showed abnormalities, like fever, the statement said.

The local government conducted complete sanitation at the patient's residence and surrounding places, and carried out a flurry of health education involving ant-rat and flea prevention, according to the statement.

Two patients from Inner Mongolia who were diagnosed with pneumonic plague in Beijing earlier this month were in critical condition in a Beijing's hospital, the National Health Commission said via its official website on Thursday. A joint medical expert group from the city and country-level are treating the patients with all medical resources.

Beijing launched a major campaign on rodent destruction starting Nov 21, which will last until the end of this month.

The city will put much effort into eliminating places that might produce various kinds of vector organisms and carry out a rodent killing winter operation, meanwhile developing health education, to the public, especially on infectious disease prevention and control, according to the capital's health authorities.

The rodent destruction operation centered on main areas, including municipal underground pipelines, public green spaces, residence communities, small and medium restaurants, hotels and farmer's markets, as well as regions that experienced epidemic hemorrhagic fever in the last two years.

Departments and communities organized by all district governments in the capital will start rodent destruction operations in a certain period of time, said the Beijing Patriotic Health Campaign Committee.

For a start, all holes connected to building exteriors should be sealed and rodent-resistant nets should be installed at the entrances of drainage pipes and ventilation pipelines, as well as some circuits.

Gaps of indoor doors and windows should be less than 0.6 centimeters and iron sheeting needs to cover the lower section of warehouse doors and storage rooms, as well as elevators. The height should be higher than 30 centimeters.