Thirty-seven people have been diagnosed with dengue fever in south China's Guangdong province, the local disease control center said on Saturday.
All 37 patients are from five localities of Zhongshan city's Huangpu township.
The Guangdong provincial disease control and prevention center said more cases are likely to be reported.
He Jianfeng, an expert at the center, said the patients had been hospitalised since July 16 with mild symptoms of muscle pain and skin rashes.
None of them had made trips to Southeast Asia, where most infections occur, indicating that the outbreak was not imported, state-run news agency Xinhua quoted him as saying.
He attributed the outbreak to rainy weather which favours breeding of the Aedes mosquito which causes dengue fever and added that the situation was under control.