NANNING -- An outbreak of hepatitis A in a middle school in Bobai county of South China's Guangxi Zhuang Autonomous Region has sent 112 students to hospital, an official said on Friday.

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All of the students have been identified as carriers of the disease, while 21 have been diagnosed as suffering from symptoms of Hepatitis A and 33 others are suspected of coming down with the disease, said Gong Jian, head of the Guangxi center for disease control and prevention.

Gong said contaminated drinking water is the main cause of the outbreak.

A well in the school, the main supply of drinking water for students, was contaminated possibly by a drainage ditch only five meters away, according to Gong.

Students also washed faces and rinsed mouths with water channeled from springs at mountains nearby.

Tests have found that colon bacillus in water from the well and springs were above the set standard, according to Gong.

Besides, the accommodation condition of students is rather poor with normally 20 students sharing one dormitory. The school's canteen was in operation without the health certificate.

The junior middle school in Bobai county has 1,438 students including some 1,000 boarders.

The first case was found on November 23 and the outbreak spread on December 6, according to the official.

A team of doctors have been vaccinating staff and students of the school after the 121 students were quarantined. They have also sterilized toilets, canteen, dormitories and classroom to stop further infection.

Gong said the outbreak is now under control.

In August, an outbreak of hepatitis A knocked down 69 high school students in South China's Guangxi Zhuang Autonomous Region.

Local epidemic prevention station's tests showed that all the water quality in the five wells which provide drinking water for the Guangxi school was far from meeting the standards for safe drinking water set by the government.

Hepatitis, or inflammation of the liver, is caused by infectious or toxic agents and characterized by jaundice, fever, liver enlargement, and abdominal pain.