The death toll from an outbreak of encephalitis B, has risen to 19, with 38 people infected in Yuncheng City of north China's Shanxi Province, the local health authorities said on Saturday.

The city reported the summer's first case of encephalitis B on July 13.The patient has recovered and has been discharged from hospital, according to the city's disease prevention and control center.

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

Nine out of the 13 counties of the city, which has a population of 5 million, have reported cases of encephalitis B, said the center.

Many people who have fallen ill come from rural areas of Yuncheng and live on flood plains of the Yellow River, where there is poor sanitation and good breeding grounds for mosquitoes, said Zhou Ying, director of the Yuncheng Health Bureau.

Yuncheng reported about 30 cases of encephalitis B patients in 2005, according to Zhou. The number of encephalitis B patients in Yuncheng accounts for over 50 percent of the total of Shanxi Province every year, he added.

Patients are now being treated in hospitals of Yuncheng and Yongji cities and Linyi County.

Among the 12 patients who are being treated at the No. 2 Hospital of Yuncheng, eight are in serious condition and doctors are trying to save their lives, said Zhang Dinglin, deputy head of the hospital.

The Shanxi Provincial Health Department has allocated 400,000 encephalitis B vaccines to Yuncheng, which had only 20,000 vaccines on hand, said Wang Jinsheng, deputy director of the center.

The vaccines will be allocated to different counties according to the severity of the epidemic, Wang said.

The vaccinations will be given away free but people will be charged three yuan (0.37 U.S. dollars) to administer the injection, Wang said.

The people in Yuncheng are being told in a media blitz to clean up their neighborhoods by sweeping away pools of standing water in which mosquitoes can breed.

Yunchang's hot weather and frequent rains have provided ideal conditions for mosquitoes to breed. As temperatures drop next month so will the number of cases of encephalitis, said Feng Lizhong, an official with the Shanxi Provincial Health Department.

Six experts from the China Disease Prevention and Control Center (CDPCC), dispatched by China's Ministry of Health, arrived in Yuncheng on Friday. They have visited patients and collected samples of the virus for laboratory analysis.

The team of experts are working with the Shanxi Provincial Health Department on urgent measures to prevent the spread of the deadly disease.

Over 80 percent of the victims found in the city are people over the age of 30, said Liang Guodong, leader of the team of experts and director of the virus research institute of the CDPCC.