Epidemiological and molecular analysis of a waterborne outbreak of norovirus GII.4.

Contaminated water is one of the main sources of norovirus (NoV) gastroenteritis outbreaks globally. Waterborne NoV outbreaks are infrequently attributed to GII.4 NoV. In September 2009, a NoV outbreak affected a small school in Guangdong Province, China. Epidemiological investigations indicated that household use water, supplied by a well, was the probable source (relative risk 1·9). NoV nucleic acid material in concentrated well-water samples was detected using real-time RT-PCR. Nucleotide sequences of NoV extracted from diarrhoea and well-water specimens were identical and had the greatest sequence identity to corresponding sequences from the epidemic strain GII.4-2006b. Our report documents the first laboratory-confirmed waterborne outbreak caused by GII.4 NoV genotype in China. Our investigations indicate that well water, intended exclusively for household use but not for consumption, caused this outbreak. The results of this report serve as a reminder that private well water intended for household use should be tested for NoV.

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

OBJECTIVE: 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. METHODS: 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. RESULTS: 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. CONCLUSION: 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.