Seven of the patients had been discharged from hospital and the others were still being treated, but none of them were described as critical and no deaths were reported, said a statement issued by Yunnan Provincial Health Bureau.

Dozens of fever patients, mostly children, were being treated in hospitals of Jiufang Township and Shidian County of Baoshan, a city in the west of the province, the statement said.

The local health authorities sent an expert panel of pediatricians to Jiufang, 44 km from Shidian, to investigate the outbreak earlier this month when many patients complained of fever, headaches and vomiting, the statement said.

According to the county government, the first patient, a nine-year-old girl, was identified on April 16, and most of the patients came from five villages of Jiufang.

The last encephalitis B outbreak to occur in Jiufang Township was in 1991.

Encephalitis B causes inflammation of the brain and can be contracted by people of all ages. It is usually the result of a viral infection transmitted to humans by mosquitoes. The illness begins with flu-like symptoms and severe headaches.