Surveillance of hepatitis A virus in urban sewages and comparison with cases notified in the course of an outbreak, Italy 2013

Abstract

BackgroundOver the past 20 years, Hepatitis A notifications in Italy have been in decline. Since the beginning of 2013 however, Italy has been experiencing a foodborne hepatitis A outbreak caused by genotype IA, involving hundreds of cases. Consumption of frozen mixed berries was deemed the potential vehicle of infection.We aimed to investigate the spread of hepatitis A virus (HAV) in Italy through the monitoring of urban sewages collected at Wastewater Treatment Plants (WTPs) and a subsequent comparison of environmental surveillance data with data from the clinical surveillance performed during the epidemic.MethodsThe study covered 15 months, from July 2012 to September 2013, comprising the outbreak and the preceding six months. Environmental surveillance consisted of the analysis of urban sewage samples collected at 19 WTPs in seven of the Italian regions most affected by the epidemic. HAV isolates were detected and typed using a nested RT-PCR targeting the VP1/2A junction. Parallel clinical surveillance was performed by the sentinel surveillance system for acute viral hepatitis (SEIEVA) and by the ministerial Central Task Force on Hepatitis A, established with the purpose of determining the source of the outbreak and adopting appropriate outbreak control strategies.ResultsA total of 38/157 wastewater samples (24.2%) were positive for HAV, 16 collected in 2012 and 22 in 2013. Several HAV strains were detected, including the IA variant implicated in the outbreak and isolated from clinical cases over the same period. The vast majority of sequences belonged to genotype IB. Interestingly however, although these included variants related to strains that had been involved in past Italian epidemics, none were detected in recent clinical samples, probably due to underreporting or asymptomatic circulation. Conversely, a number of sequences were identified in clinical samples that were not found in wastewaters.ConclusionsThe percentage of sewage samples detected as HAV-positive in this study are consistent with the classification of Italy as a country with low/intermediate endemicity. A combined environmental/clinical surveillance is able to provide a more complete picture of the spread of HAV and of the genotypes circulating in the population, allowing a better understanding of changes in disease trends.Electronic supplementary materialThe online version of this article (doi:10.1186/1471-2334-14-419) contains supplementary material, which is available to authorized users.

Hepatitis A and E Viruses in Wastewaters, in River Waters, and in Bivalve Molluscs in Italy

“…1. The tree includes, in addition to the study sequences, 10 GeneBank prototype sequences corresponding to genotypes IA, IB, IIA, IIB, IIIA, and IIIB, and IA and IB sequences previously detected in sewage samples in Italy (La Rosa et al 2014). In addition, the sequence KF182323, prototype of the Italian 2013 outbreak (Rizzo et al 2013), and still unpublished sequences from clinical cases collected during the epidemic, are reported.…”

Qualitative and Quantitative Assessment of Hepatitis A Virus in Wastewaters in Tunisia

“…In our study, the percentage of HAVpositive raw sewage samples (68 %) appears to be consistent with the classification of the country as having an intermediate/high level of HAV endemicity. Indeed, studies from low/intermediate endemicity areas revealed relatively low percentages of HAV-positive samples in urban wastewaters in recent years, ranging from 3.1 % to 26 % (La Rosa et al 2014;Pinto et al 2007;Rodriguez-Manzano et al 2010), whereas studies from high-endemicity areas yielded considerably higher percentages of HAV-positive sewage samples, up to 88 % (Pinto et al 2007;Prado et al 2012;Villar et al 2007).…”

Detection and Molecular Characterization of Hepatitis A Virus from Tunisian Wastewater Treatment Plants with Different Secondary Treatments

“…Subgenotype IA appears to be the most prevalent variant worldwide, whereas in Europe and the Mediterranean region, a more heterogeneous pattern has been found, with cocirculation of the subgenotypes IA and IB (17,20,21). It has been demonstrated that the subgenotype IA strain was predominant in Tunisia, while subgenotype IB was rarely detected (4,22).…”

“…Unfortunately, Tunisia, among other Mediterranean countries with high endemicity of HAV infections, is using contaminated treated wastewater for irrigation and to refill aquifers to palliate the lack of water resources (14), which may pose a real threat for public health. Indeed, the lack of a specific system in Tunisia for surveillance of HAV or other enteric viruses in wastewaters (15) and the changing epidemiology of HAV (16) are among the many risk factors (3,5,12,17) that increase the potential human risk associated with viral contamination in wastewater. …”