An infectious hepatitis A outbreak struck 39 students at a primary school in central China's Hunan Province and medical experts say the epidemic was probably caused by unboiled water, provincial health authorities announced Tuesday.

After an epidemiological investigation and relevant medical tests, the provincial department of health confirmed that 39 students at Fugui Primary School at Guanling Town, Changning City, were infected with hepatitis A.

A spokesman for the department said the epidemic was under " effective control" as the epidemic was not reported among the sick students' family members or other teaching faculty and villagers nearby.

The school reported its first case of hepatitis A on April 26 and no new cases had been reported since May 11, according to an investigation report released by the provincial health department.

The medical report said the outbreak at the school were probably caused by unboiled water as all the sick students had the habit of drinking unboiled water directly taken from a well at the school.

The primary school with 645 students and 29 teachers relies on their own well for water supply, teachers at the school said.

Hepatitis A is a liver disease caused by the hepatitis A virus and it can affect anyone if good personal hygiene and proper sanitation measures are not taken, doctors said.

Vaccines are also available for long-term prevention of the disease in persons two years of age and older. Immune globulin is available for short-term prevention of hepatitis A virus infection in individuals of all ages.