Detection of pathogenic viruses in sewage provided early warnings of hepatitis A virus and norovirus outbreaks

Abstract

Most persons infected with enterically transmitted viruses shed large amounts of virus in feces for days or weeks, both before and after onset of symptoms. Therefore, viruses causing gastroenteritis may be detected in wastewater, even if only a few persons are infected. In this study, the presence of eight pathogenic viruses (norovirus, astrovirus, rotavirus, adenovirus, Aichi virus, parechovirus, hepatitis A virus [HAV], and hepatitis E virus) was investigated in sewage to explore whether their identification could be used as an early warning of outbreaks. Samples of the untreated sewage were collected in proportion to flow at Ryaverket, Gothenburg, Sweden. Daily samples collected during every second week between January and May 2013 were pooled and analyzed for detection of viruses by concentration through adsorption to milk proteins and PCR. The largest amount of noroviruses was detected in sewage 2 to 3 weeks before most patients were diagnosed with this infection in Gothenburg. The other viruses were detected at lower levels. HAV was detected between weeks 5 and 13, and partial sequencing of the structural VP1protein identified three different strains. Two strains were involved in an ongoing outbreak in Scandinavia and were also identified in samples from patients with acute hepatitis A in Gothenburg during spring of 2013. The third strain was unique and was not detected in any patient sample. The method used may thus be a tool to detect incipient outbreaks of these viruses and provide early warning before the causative pathogens have been recognized in health care.

FIG 1

Variations in real time of the inflow of sewage to the treatment plant Ryaverket, Gothenburg, Sweden, for the study period between 12 January 2013 and 20 April 2013. Dates are given in the format year-month-day.

FIG 2

Estimation of the number of infected persons that secrete norovirus GII daily during weeks 5, 7, 9, 11, and 13 in 2013 based on the number of viruses identified in the weekly wastewater samples (assuming an infected person shed 10¹¹ particles per day) and the number of patients diagnosed as infected with norovirus GII in the corresponding weeks.

FIG 3

Phylogenetic tree based on 465 nucleotides of the N-terminal part of VP1 in the HAV genome. Shown is the branch with HAV IB strains identified in patients and sewage from Gothenburg. Patient samples are marked in blue and sewage samples and outbreak strains in red.

FIG 4

Phylogenetic tree based on 465 nucleotides of the N-terminal part of VP1 in the HAV genome. The tree shows part of the HAV IB branch. The identified strain from sewage collected during week 5 in 2013 at Ryaverket, Gothenburg, Sweden, is shown in red.