Health Stream Literature Summary - Issue 55 - September 2009

First Molecular Detection of Group A Rotaviruses in Drinking Water Sources in Beijing, China.
He, X.Q., Cheng, L., Zhang, D.Y., Li, W., Xie, X.M., Ma, M. and Wang, Z.J. (2009) Bulletin of Environmental Contamination and Toxicology, 1-5.

Group A rotaviruses are the main cause of acute viral gastroenteritis in infants and young children worldwide. In Beijing China, rotavirus has been detected in nearly 60% of all diarrheal patients and group A rotaviruses have been shown to be a significant cause of sporadic and epidemic paediatric gastroenteritis. Rotaviruses may contaminate source waters through sewage overflows or poorly functioning sewage systems, and their stability and resistance to physiochemical treatment processes may facilitate their transmission through water. In China, water quality evaluation does not require testing for rotavirus, and the role of drinking water in rotavirus transmission is unknown. This study investigated whether rotavirus group A found in children’s diarrheic samples was present in raw water sources, treated water and tap water.

There were 26 raw water samples, 77 treated drinking water samples and 143 tap water samples collected from April 2006 to August 2007 in Beijing. Raw water samples were taken from acceptable quality reservoirs, lakes and groundwater sources serving the water works in Beijing which conformed to national specifications for the production of safe tap water. Treated water was collected from several water works after treatment which consisted of chemical feed, coagulation, flocculation, sedimentation, rapid gravity filtration, activated carbon adsorption and chlorination. Tap water from different water works was taken systematically in a public area chosen for its easy access (school or city hall) within the city limits. Amplification of viral RNA in water samples was undertaken by RT-nested PCR. Total coliform (TC), faecal coliform (FC) and Streptococcus faecalis were enumerated using a membrane filtration method following standard protocols. The pH of the water was measured on site and residual chlorine was measured.

Group A rotaviruses occurred in 9 of 26 (34.6%) raw water samples, 9 of 77 (11.7%) treated water samples and 32 of 143 (22.4%) tap water samples during the sampling period. The 9 positive results in raw water and treated water samples were all for samples collected during October 2006, and positive results were also found for all 11 tap water samples collected at the same time. The remaining 21 positive tap water samples were collected from November 2006 to January 2007. These results correspond with the previously reported seasonal peak in rotavirus infection occurring during the winter months in Beijing. The pH range for drinking water samples was 6.5 to 8.5, with one raw water sample over 8.0. The residual chlorine levels in treated drinking water conformed with the National Standards for Drinking Water in China (greater than or equal to 0.3 mg L-1) and the tap water samples from distribution system were a little higher than or equal to 0.05 mg L-1 (the minimum required in the Standards). All the tap water was found to be of acceptable microbiological quality according to heterotrophic plate counts, TC, FC as well as Streptococcus.

This study demonstrated that raw water was contaminated with rotavirus which was not adequately removed by treatment, however additional sources of contamination in the distribution system may also have existed. This study showed that bacterial indicators of water quality did not adequately reflect the occurrence of group A rotaviruses in the aquatic environment. The results found here provide new information on rotaviruses in water and highlight the potential of waterborne transmission in Beijing and the potential threat to public health. There is a need for further surveillance of aquatic environments to identify the strains of rotavirus circulating in the community and to implement appropriate preventive control measures.

Comment In this study rotaviruses were detected by molecular methods rather than cell culture or combined culture-PCR, so it is not known what fraction of virus particles were infectious. The results of this study are not sufficient to estimate what proportion of rotavirus infections in Beijing may be attributable to waterborne transmission.

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