Epidemiological investigation of a tap water-mediated hepatitis E virus genotype 4 outbreak in Zhejiang Province, China

Abstract

An outbreak of acute hepatitis recently occurred in a nursing home in Zhejiang Province, China. The objectives of this study were to confirm the outbreak and identify the aetiology, source and transmission patterns. All residents and staff in or near the nursing home during the period from 1 October 2014 to 21 May 2015 were investigated regarding hygiene and for epidemiological information including water and food (eating meat especially pork products). Serum and stool specimens were collected for detection of hepatitis E virus (HEV) antibodies using ELISA and RNA using RT-PCR. Samples that were RNA positive were genotyped. Of 185 senior residents and 24 staff in the nursing home, there were 37 laboratory-confirmed cases during the outbreak. Of these cases, 12 patients (three deaths) were symptomatic with jaundice, a common clinical symptom for hepatitis E infection. HEV strains were isolated from three cases and they formed a single cluster within genotype 4d. A case-control study was conducted to investigate potential risk factors for the outbreak and the results revealed that cases more often washed their dishes and rinsed their mouths using tap water than the controls (P < 0·05). Based on hygiene investigation and meteorological information, it is likely that HEV-infected sewage and faeces contaminated the water network on rainy days. Collectively, these results suggest that the outbreak of HEV genotype 4 infection was most likely caused by contaminated tap water rather than food.

A systematic review on the causes of the transmission and control measures of outbreaks in long-term care facilities: Back to basics of infection control

“…Six studies were at low risk for all criteria [15][16][17][18][19][20]. Problems related to recall bias and standardization of self-reported measurement created a high risk of bias for the measurement of the exposure domain in seven studies [14,[21][22][23][24][25][26]. Lack of consideration for confounders led to a high risk of bias in four studies [24,[27][28][29].…”

“…Characteristics of the outbreaks are presented in Tables 2-4. Fifteen studies reported outbreaks caused by bacteria [15-17, 20, 22, 24, 27, 32-39] and 22 studies were outbreaks by viruses [14,18,19,21,23,25,26,[28][29][30][31][40][41][42][43][44][45][46][47][48][49][50]. The largest number of a single pathogen was influenza viruses [40][41][42][43][44][45], followed by group A streptococcus (GAS) [17,20,24,37,38].…”

“…Three studies analyzed the data of multiple outbreaks of viral gastroenteritis and influenza-like illness that occurred in multiple facilities for a certain period of time [14,46,48]. The outbreaks in 23 studies affected both the residents and HCWs [14,20,22,23,25,26,29,31,33,[35][36][37][38][39][40][41][43][44][45][46][47][48][49], and the outbreaks of 14 studies affected only the residents [15-19, 21, 24, 27, 28, 30, 32, 34, 42, 50].…”

“…In the study by Šubelj and Učakar [23], person-to-person transmission resulted from delayed implementation of control measures. Contaminated water and food were sources of infection in five studies [16,25,26,33,46]. Hepatitis E outbreak was caused by contaminated tap water after heavy rain [25], while the consumption of tap water was the suspected cause of one viral gastroenteritis outbreak [26].…”

“…Contaminated water and food were sources of infection in five studies [16,25,26,33,46]. Hepatitis E outbreak was caused by contaminated tap water after heavy rain [25], while the consumption of tap water was the suspected cause of one viral gastroenteritis outbreak [26]. Foodborne causes such as contaminated cake or meals were noted in three studies regarding Clostridium perfringens, Salmonella enteritidis, and gastroenteritis [16,33,46].…”