KUNMING, Aug. 22 (Xinhua) -- Thirty one new cases of dengue fever were confirmed in a prefecture of southwest China's Yunnan province, raising the total to 154, the local government announced on Thursday.

Between 4 p.m. Tuesday to 4 p.m. Wednesday, the Dai Autonomous Prefecture of Xishuangbanna saw an increase of 31 dengue cases, including one returned from abroad, said the prefectural government.

Among the 154 cases, five were infected aboard. No serious cases or deaths have been reported since first reports from the area a week ago.

Xishuangbanna has started a Grade III emergency response to the epidemic. Experts from the Chinese Center for Disease Control and Prevention and the provincial health department have gone to the area to help control the outbreak.

Local health authorities and police have been mobilized to control the spread of the disease. Quarantine authorities have strengthened monitoring of people coming and going from the area.

Dengue is a mosquito-borne, potentially fatal disease that affects between 50 and 100 million people in tropical and subtropical regions every year, causing fever and muscle and joint aches.