A hepatitis A outbreak caused by contaminated well water in a primary school of Jiangxi province, China, 2009

Abstract

A hepatitis A outbreak in a primary school was reported by Gan County Center for Disease Control and Province (CDC) and an investigation was conducted to identify the possible source of infection and risk factors for transmission. A probable case was defined as having onset of jaundice (yellow urine, sclera or skin) or a 2-fold increase in Alanine aminotransferase with 2 or more, of the followings symptoms: anorexia, disgust of oil, abdominal pain, nausea, fatigue, vomiting, in students and staff of the primary school between 1 November 2008 and 14 February 2009. A confirmed case was IgM positive for hepatitis A, added on a probable case. We searched for cases through reviewing medical records in the township hospital and village clinics and conducting symptom screening among students or teachers. We also conducted a case-control study to compare the exposure histories of 19 cases and 53 anti-HAV-IgM negative controls randomly selected from those asymptomatic students in the same grade. 21 cases from all the students was identified, with the attack rate as 3.5%. The epidemic curve showed the two peaks of the outbreak were 28 days apart, both indicating that they were related to the exposure of the source of origin. 74% of the case-students drank the unboiled Well B water, compared to 42% of control-students (OR = 4.0, 95%CI: 1.1 - 15). The total bacterial count was 600 cfu/ml and the total coliform was 23 MPN/100 ml in one sample collected from the well water. This hepatitis A outbreak was caused by drinking contaminated water in Well B. We recommended that all the schools should use chlorinated municipal pipe water. Public health authorities should strengthen the supervision of quality of water in schools.