Extensive immunization programs have been carried out in Qinghai Province, northwest China, after a rare case of polio was found last month in an ethnic rural area.

Some 134 medical workers have been sent to 154 villages in ten towns of the Salar Autonomous County of Xunhua, where the rare polio case was found, to contain the disease and ensure that all children are vaccinated.

A 18-month-old boy in the town of Jiezi was the first reported case. The virus is believed to have been brought in from outside China.

Health experts are still not sure when and how the virus was brought into the country, where the last reported polio case was in 1994.

Zhou Maojia, deputy director of the Xunhua Health Bureau, has paid a visit to the 18-month-old boy, and has asked local health department to remain vigilant.

Polio often inflicts children and young adults. It is an acute infectious disease that attacks the motor nerves of the spinal cord and brain stem, and sometimes results in muscular atrophy and skeletal deformity.