According to official sources Japanese encephalitis has to date claimed 19 lives in the northern Chinese city of Yuncheng in the Shanxi province.

Local health authorities say 740,000 vaccines are urgently needed to inoculate all residents of the province under the age of 20, but they have at present only secured 400,000 vaccines.

As more than 20% of the city’s population of about 5 million are under the age of 20, authorities have resorted to approaching pharmaceutical companies for help.

Although the vaccinations will be given away free, people will be charged for the injection.

Nine out of the 13 counties of the city are now affected but authorities say the outbreak is under control.

An official with the National Disease Prevention and Control Center says up to 60 people had been infected with the disease, 19 had died and another 31 remained in hospital; eight of those are reported to be in a critical condition and 6 others have recovered and been discharged from hospital.

This compares with 30 cases in 2005 and the local media is being used to encourage people to clean up their neighbourhoods by clearing away pools of standing water in which mosquitoes can breed.

Yuncheng is a rural area and many people live on the flood plains of the Yellow River, where poor sanitation ensures ideal breeding conditions for mosquitoes.

Domestic pigs and wild birds are reservoirs of the virus and the transmission to humans may cause severe symptoms.

Japanese encephalitis causes an inflammation of the membranes around the brain, and it can be contracted by people of all ages.

It is as a rule the result of a viral infection passed to humans by mosquitoes and is not transmitted between humans.

The illness begins with flu-like symptoms and severe headaches.

According to the World Health Organization, 50,000 cases of Japanese encephalitis are recorded in Asia each year, resulting in 15,000 deaths and permanent disability for many.