Key Role of Sequencing to Trace Hepatitis A Viruses Circulating in Italy During a Large Multi-Country European Foodborne Outbreak in 2013

Abstract

BackgroundFoodborne Hepatitis A Virus (HAV) outbreaks are being recognized as an emerging public health problem in industrialized countries. In 2013 three foodborne HAV outbreaks occurred in Europe and one in USA. During the largest of the three European outbreaks, most cases occurred in Italy (>1,200 cases as of March 31, 2014). A national Task Force was established at the beginning of the outbreak by the Ministry of Health. Mixed frozen berries were early demonstrated to be the source of infection by the identity of viral sequences in patients and in food. In the present study the molecular characterization of HAV isolates from 355 Italian cases is reported.MethodsMolecular characterization was carried out by PCR/sequencing (VP1/2A region), comparison with reference strains and phylogenetic analysis.ResultsA unique strain was responsible for most characterized cases (235/355, 66.1%). Molecular data had a key role in tracing this outbreak, allowing 110 out of the 235 outbreak cases (46.8%) to be recognized in absence of any other link. The data also showed background circulation of further unrelated strains, both autochthonous and travel related, whose sequence comparison highlighted minor outbreaks and small clusters, most of them unrecognized on the basis of epidemiological data. Phylogenetic analysis showed most isolates from travel related cases clustering with reference strains originating from the same geographical area of travel.ConclusionsIn conclusion, the study documents, in a real outbreak context, the crucial role of molecular analysis in investigating an old but re-emerging pathogen. Improving the molecular knowledge of HAV strains, both autochthonous and circulating in countries from which potentially contaminated foods are imported, will become increasingly important to control outbreaks by supporting trace back activities, aiming to identify the geographical source(s) of contaminated food, as well as public health interventions.

Hepatitis A virus strains circulating during 1997-2015 in Campania, a Southern Italy region with periodic outbreaks

“…NC_001489) of the VP1/2A junction was chosen for genotyping and phylogenetic analysis. This region of HAV was amplified by a nested RT‐PCR reaction as reported . Sequences were obtained by double strand sequencing of the purified PCR products using the GenomeLab DTCS Quick Start Kit and an automated DNA sequencer (Beckman Coulter, Inc., Fullerton, CA).…”

“…Due to improvements in hygiene and living conditions, Italy is currently considered a country with low/intermediate level of HAV endemicity. The incidence of acute hepatitis A has declined over time in Italy decreasing from 19 cases per 100 000 population in 1997 to 0.6 cases per 100 000 population in 2015 (data from SEIEVA, the Italian integrated epidemiological system for acute viral hepatitis, available at: http://www.iss.it/binary/seie2/cont/Tassi_EpatiteA_2015.pdf), a decline not homogeneous throughout the country mostly because of frequent outbreaks of various origin occurred in some regions . Particularly, in Campania and Apulia (Southern Italy) high annual incidence rates have been reported and several periodic outbreaks have occurred …”

Monitoring of Foodborne Hepatitis A virus Outbreaks in the Fresh Foods

“…In the case of environmental samples, amplification of viral nucleic acids by polymerase chain reaction (PCR) assays coupled to reverse transcription (RT-PCR) has been used in water and shellfish. (Vasickova et al, 2005 andBruni et al, 2016). The molecular characterization is as an essential tool to trace HAV outbreaks (Bruni et al, 2016); mixed frozen berries were early demonstrated to be the source of HAV infection by the identity of viral sequences in patients and in food.…”

“…(Vasickova et al, 2005 andBruni et al, 2016). The molecular characterization is as an essential tool to trace HAV outbreaks (Bruni et al, 2016); mixed frozen berries were early demonstrated to be the source of HAV infection by the identity of viral sequences in patients and in food.…”

“…EL DOUGDOUG et al et al, 2000). Recent food-borne outbreaks of hepatitis A have been associated with different types of canned soft fruit like strawberries (Anonymous, 1997), vegetables like green onions and lettuces (Bidawid et al, 2000) and frozen berries (Bruni et al, 2016). HAV is considered one of the most common illnesses through oralfecal infection special in children and olds in poor developing country (Fan et al, 2006).…”