Viruses and bivalve shellfish

Accumulation of a low pathogenic avian influenza virus in zebra mussels (Dreissena polymorpha)

In order to investigate the potential role of mussels as a vector of influenza A viruses, we exposed zebra mussels (Dreissena polymorpha) to natural lake water containing a low pathogenic H5N1 avian influenza virus. Mussels were kept in water containing virus for 48 hr, then transferred into fresh water for another 14 days. Virus detection in mussels and water samples was performed by quantitative real-time reverse transcriptase-PCR (qRRT-PCR) and egg culture methods. Virus uptake was detected in all of the mussel groups that were exposed to virus. Even after 14 days in fresh water, virus could still be detected in shellfish material by both qRRT-PCR and egg culture methods. The present study demonstrates that zebra mussels are capable of accumulating influenza A viruses from the surrounding water and that these viruses remain in the mussels over an extended period of time.

Norovirus, hepatitis A virus and enterovirus presence in shellfish from high quality harvesting areas in Portugal

This is the first report on the screening of shellfish from Portugal for the presence of human enteropathogenic viruses. Approximately 2000 shellfish (Curbicula fluminea, Ruditapes decussatus, Tellina crassa, Spisula solida, Dosinia exoleta, Ensis spp., Mytilus spp., Ostrea edulis and Cerastoderma edule), organized in 49 batches, were collected between March 2008 and February 2009. They were tested for norovirus (NoV), hepatitis A virus (HAV) and enterovirus (EV) by RT-PCR followed by nucleotide sequencing. Bacterial contamination was also evaluated by Escherichia coli counts. Viral contamination was detected throughout the year in all shellfish species and in all collection areas, independently of their harvesting areas classification. Overall, 67% of all analyzed batches were contaminated by at least one of the studied viruses while the simultaneous presence of two and three viruses was detected in 22% and 6% batches, respectively. Of the three viruses, NoV was detected in 37% of the batches, followed by EV in 35%, and HAV in 33%. Nucleotide sequencing of the NoV and HAV RT-PCR products demonstrated that all strains belonged to NoV genotype GII.4 and HAV subgenotype 1B. The presence of NoV and HAV in shellfish from "A class" harvesting areas of Portugal can represent a potential health risk.

Surveillance of adenoviruses and noroviruses in European recreational waters

Exposure to human pathogenic viruses in recreational waters has been shown to cause disease outbreaks. In the context of Article 14 of the revised European Bathing Waters Directive 2006/7/EC (rBWD, CEU, 2006) a Europe-wide surveillance study was carried out to determine the frequency of occurrence of two human enteric viruses in recreational waters. Adenoviruses were selected based on their near-universal shedding and environmental survival, and noroviruses (NoV) selected as being the most prevalent gastroenteritis agent worldwide. Concentration of marine and freshwater samples was done by adsorption/elution followed by molecular detection by (RT)-PCR. Out of 1410 samples, 553 (39.2%) were positive for one or more of the target viruses. Adenoviruses, detected in 36.4% of samples, were more prevalent than noroviruses (9.4%), with 3.5% GI and 6.2% GII, some samples being positive for both GI and GII. Of 513 human adenovirus-positive samples, 63 (12.3%) were also norovirus-positive, whereas 69 (7.7%) norovirus-positive samples were adenovirus-negative. More freshwater samples than marine water samples were virus-positive. Out of a small selection of samples tested for adenovirus infectivity, approximately one-quarter were positive. Sixty percent of 132 nested-PCR adenovirus-positive samples analysed by quantitative PCR gave a mean value of over 3000 genome copies per L of water. The simultaneous detection of infectious adenovirus and of adenovirus and NoV by (RT)PCR suggests that the presence of infectious viruses in recreational waters may constitute a public health risk upon exposure. These studies support the case for considering adenoviruses as an indicator of bathing water quality.

Human norovirus RNA persists in seawater under simulated winter conditions but does not bioaccumulate efficiently in Pacific Oysters (Crassostrea gigas)

Norovirus (NoV) is the principal agent of bivalve molluscan shellfish-associated gastroenteric illness worldwide. Currently, noncultivable human NoVs can be detected in bivalve molluscan shellfish by using molecular methods such as real-time reverse transcription PCR assays (qRT-PCR). In addition to infectious viruses, this methodology may also detect noninfectious NoV, including fragments of the NoV genome. This study addresses, in part, the implications of qRT-PCR results for the detection of NoV in shellfish in the absence of an infectivity assay. To evaluate environmental persistence, the stability of a short fragment of the NoV genome, spanning the qRT-PCR target in the open reading frame 1/2 junction, was assessed in seawater under artificial environmental conditions simulating winter in the United Kingdom (1 mW/cm² UV irradiation, 8°C) during a 4-week period. Detectable RNA levels decreased exponentially (T₉₀ of approximately 141 h); however, sequences were still detectable for up to 2 weeks. The ability of Pacific oysters (Crassostrea gigas) to bioaccumulate NoV particles (from human feces) and RNA fragments was also compared using qRT-PCR. Oysters exposed to NoV particles subsequently were positive for NoV by qRT-PCR at levels several orders of magnitude in excess of the theoretical limit of detection, whereas oysters exposed to similar quantities of NoV RNA were either negative or positive at significantly lower levels. Therefore, although noninfectious fragments of NoV RNA may persist in the environment under winter conditions, this type of material will not be efficiently bioaccumulated by Pacific oysters and should not significantly contribute to positive qRT-PCR results.

Detection of cyprinid herpesvirus-3 DNA in lake plankton

The disease caused by cyprinid herpesvirus-3 (CyHV-3) severely impacts the natural freshwater ecosystem and damages carp and koi farming, however, the pathway of CyHV-3 transmission remains unclear. It is possible that the virus adheres to plankton, which then facilitate viral movement and transmission, and therefore, it is hypothesised that plankton are involved in the disease dynamics. In this study, plankton were collected at eight sites in the Iba-naiko lagoon; we detected and quantified CyHV-3 DNA from plankton samples. The results of the correlation analysis showed a significant positive correlation between CyHV-3 copies and the number of Rotifera, suggesting that CyHV-3 binds to and/or is concentrated by Rotifera. Our results suggest that plankton affect viral ecology in the natural environment.

Avian influenza virus in aquatic habitats: what do we need to learn?

Although aquatic habitats utilized by wild and domestic birds potentially can provide a bridge for avian influenza virus (AIV) transmission among many diverse hosts, the factors controlling environmental persistence and transmission via these habitats are poorly understood. AIV has been detected in water samples collected in the field, and under experimental laboratory conditions, these viruses can remain infective in water for periods of time that would be consistent with an environmental reservoir. However, the application of laboratory results to field realities is complicated by the complexity and scale of these systems. In this brief review, we present a summary of existing research on the environmental tenacity of AIV, provide an example of the challenges associated with the application of laboratory results to the field realities associated with detection of AIV from environmental sources, and identify gaps in our current understanding of the factors potentially affecting AIV infectivity in the environment, specifically from aquatic habitats utilized by wild birds.

Comparison between quantitative real-time reverse transcription PCR results for norovirus in oysters and self-reported gastroenteric illness in restaurant customers

Norovirus is the principal agent of bivalve shellfish-associated gastroenteric illness worldwide. Numerous studies using PCR have demonstrated norovirus contamination in a significant proportion of both oyster and other bivalve shellfish production areas and ready-to-eat products. By comparison, the number of epidemiologically confirmed shellfish-associated outbreaks is relatively low. This study attempts to compare norovirus RNA detection in Pacific oysters (Crassostrea gigas) by quantitative real-time reverse transcription PCR (RT-PCR) and human health risk. Self-reported customer complaints of illness in a restaurant setting (screened for credible norovirus symptoms) were compared with presence and levels of norovirus as determined by real-time RT-PCR for the batch of oysters consumed. No illness was reported for batches consistently negative for norovirus by real-time RT-PCR. However, norovirus was detected in some batches for which no illness was reported. Overall presence or absence of norovirus showed a significant association with illness complaints. In addition, the batch with the highest norovirus RNA levels also resulted in the highest rate of reported illness, suggesting a linkage between virus RNA levels and health risks. This study suggests that detection of high levels of norovirus RNA in oysters is indicative of a significantly elevated health risk. However, illness may not necessarily be reported after detection of norovirus RNA at low levels.

Viral Inactivation in Foods: A Review of Traditional and Novel Food-Processing Technologies

  Over one-half of foodborne illnesses are believed to be viral in origin. The ability of viruses to persist in the environment and foods, coupled with low infectious doses, allows even a small amount of contamination to cause serious problems. An increased incidence of foodborne illnesses and consumer demand for fresh, convenient, and safe foods have prompted research into alternative food-processing technologies. This review focuses on viral inactivation by both traditional processing technologies such as use of antimicrobial agents and the application of heat, and also novel processing technologies including high-pressure processing, ultraviolet- and gamma-irradiation, and pulsed electric fields. These industrially applicable control measures will be discussed in relation to the 2 most common causes of foodborne viral illnesses, hepatitis A virus and human noroviruses. Other enteric viruses, including adenoviruses, rotaviruses, aichi virus, and laboratory and industrial viral surrogates such as feline caliciviruses, murine noroviruses, bacteriophage MS2 and ΦX174, and virus-like particles are also discussed. The basis of each technology, inactivation efficacy, proposed mechanisms of viral inactivation, factors affecting viral inactivation, and applicability to the food industry with a focus on ready-to-eat foods, produce, and shellfish, are all featured in this review.

Risk assessment in shellfish-borne outbreaks of hepatitis A

In the present work, we aimed at determining the relationship between the hepatitis A virus (HAV) numbers in imported frozen coquina clams involved in two hepatitis outbreaks, as well as the risk for human health. Due to HAV unculturability, a standardized TaqMan real-time reverse transcription-PCR controlling the virus/nucleic acid extraction and enzyme efficiencies was employed to figure the exposure dose for clams responsible for hepatitis cases. HAV numbers were then employed to figure the risk of infection based on a dose-response model for echovirus 12. The estimated risk of infection after consumption of lightly cooked clams matched actual attack rates. Our data show that prospective monitoring of bivalve samples may fail to prevent the occurrence of outbreaks, since HAV was detected in 44% of samples directly associated with cases but was undetectable in samples that were randomly collected from the importers and belonged to the same batches. A correlation was nevertheless observed between the prevalence of hepatitis A cases in the harvesting areas and positive HAV isolation in clams, which points to the need to identify and prevent hazards rather than relying on random sampling of finished products to ensure safety. However, when evidence shows that a critical limit of viral contamination has been exceeded in the potential sources of contamination discharging into the shellfish-growing beds, quantitative virological analysis addressing quality assurance and quality control requirements should be performed with the bivalves. This work provides the first evidence of accurate HAV levels in shellfish involved in outbreaks that could be of use for risk assessment purposes.

Effects of technological processes on the tenacity and inactivation of norovirus genogroup II in experimentally contaminated foods

Contaminated food is a significant vehicle for human norovirus transmission. The present study determined the effect of physicochemical treatments on the tenacity of infective human norovirus genogroup II in selected foods. Artificially contaminated produce was subjected to a number of processes used by the food industry for preservation and by the consumer for storage and preparation. Virus recovery was carried out by using ultrafiltration and was monitored by using bacteriophage MS2 as an internal process control. Norovirus was quantified by using monoplex one-step TaqMan real-time reverse transcription (RT)-PCR and an external standard curve based on recombinant RNA standards. An RNase pretreatment step was used to avoid false-positive PCR results caused by accessible RNA, which allowed detection of intact virus particles. Significant reductions in titers were obtained with heat treatments usually applied by consumers for food preparation (baking, cooking, roasting). Generally, processes used for preservation and storage, such as cooling, freezing, acidification (>or=pH 4.5), and moderate heat treatments (pasteurization), appear to be insufficient to inactivate norovirus within a food matrix or on the surface of food. Besides data for persistence in processed food, comparable data for individual matrix-specific protective effects, recovery rates, and inhibitory effects on the PCRs were obtained in this study. The established procedure might be used for other noncultivable enteric RNA viruses that are connected to food-borne diseases. The data obtained in this study may also help optimize the process for inactivation of norovirus in food by adjusting food processing technologies and may promote the development of risk assessment systems in order to improve consumer protection.

Use of FRNA bacteriophages to indicate the risk of norovirus contamination in Irish oysters

Male-specific (F) RNA bacteriophages have been proposed as indicators for human enteric viruses in shellfish. This study compared the use of Escherichia coli and FRNA bacteriophages to indicate the presence and level of noroviruses in Crassostrea gigas. A total of 167 samples from category A and B shellfish harvesting areas were analyzed for E. coli and FRNA bacteriophages by standard methods and for noroviruses (NoV) by using a previously described real-time PCR assay. FRNA bacteriophage and NoV levels in shellfish showed a seasonal trend and were elevated during the winter period (October through March). Conversely, E. coli levels did not reflect this seasonal trend. Categorizing samples on the basis of E. coli levels according to European Union regulatory limits failed to indicate the occurrence or level of NoV in shellfish. However, by grouping shellfish samples on the basis of FRNA bacteriophage levels a clear correlation was observed with NoV levels. The use of FRNA bacteriophages to predict the occurrence of NoV in shellfish could provide improved public health protection and should be considered when developing risk management procedures for shellfisheries.

Genetic heterogeneity and recombination in canine noroviruses

Alphatronlike (genogroup IV [GIV]) noroviruses (NoVs) have been recently identified in carnivores. By screening a collection of 183 fecal samples collected during 2007 from dogs with enteric signs, the overall NoV prevalence was found to be 2.2% (4/183). A unique strain, Bari/91/07/ITA, resembled GIV.2 NoVs in its ORF1 (polymerase complex), while it was genetically unrelated in its full-length ORF2 (capsid gene) to GIV animal and human NoVs (54.0 to 54.4% amino acid identity) and to any other NoV genogroup (<54.7% amino acid identity). It displayed the highest identity (58.1% amino acid identity) to unclassified human strain Chiba/040502/04/Jp. Interestingly, the very 5' end of ORF2 of the canine virus matched short noroviral sequences (88.9% nucleotide identity and 98.9% amino acid identity) identified from oysters in Japan, indicating that similar viruses may be common environmental contaminants.

Filter-feeding bivalves can remove avian influenza viruses from water and reduce infectivity

Avian influenza (AI) viruses are believed to be transmitted within wild aquatic bird populations through an indirect faecal-oral route involving contaminated water. This study examined the influence of filter-feeding bivalves, Corbicula fluminea, on the infectivity of AI virus in water. Clams were placed into individual flasks with distilled water inoculated 1:100 with a low pathogenic (LP) AI virus (A/Mallard/MN/190/99 (H3N8)). Viral titres in water with clams were significantly lower at 24 and 48 h post-inoculation compared to LPAI-infected water without clams. To determine whether clams affected the infectivity of AI viruses, 18 wood ducks (Aix sponsa) were divided into test groups and inoculated with a variety of treatments of clam supernatants, whole clams and water exposed to a high pathogenic (HP) AI (A/whooper swan/Mongolia/244/05 (H5N1)). None of the wood ducks inoculated with HPAI-infected water that was filtered by clams or that was inoculated with or fed tissue from these clams exhibited morbidity or mortality. All wood ducks exposed to either HPAI-infected water without clams or the original viral inoculum died. These results indicate that filter-feeding bivalves can remove and reduce the infectivity of AI viruses in water and demonstrate the need to examine biotic environmental factors that can influence AI virus transmission.

Norovirus in retail shellfish

Norovirus is a common cause of gastroenteritis outbreaks associated with consumption of raw shellfish. The majority of norovirus infections worldwide are due to genogroup II noroviruses. Bivalve molluscs (mussels, clams and oysters) at the end of the commercial chain, the points of purchase, were sampled between 2005 and 2008 in several retail points in Apulia, Italy, and screened by a semi-nested RT-PCR specific for genogroup II noroviruses. Noroviral RNA was detected in 12.1% of the samples, with lower frequency being observed in samples obtained from hypermarkets (8.1%) rather than in samples from open-air markets and fish shops (17.6% and 16.2%, respectively). By sequence analysis, the strains were characterized as norovirus variants GII.4/2004 and GII.b/Hilversum, which were both circulating in Italy in the same time-span.

Inactivation and elimination of human enteric viruses by Pacific oysters

AIMS

To investigate the comparative elimination of three different human enterically transmitted viruses [i.e. hepatitis A virus (HAV), norovirus (NoV) and poliovirus (PV)] and inactivation of HAV and PV by Pacific oysters.

METHODS AND RESULTS

New Zealand grown Pacific oysters (Crassostrea gigas) were allowed to bioaccumulate HAV, NoV and PV. Samples of oyster gut, faeces and pseudofaeces were then analysed by using real-time RT-PCR to determine the amount of viral RNA and cell culture methods to identify changes in the number of plaque forming units. The results suggest that the majority of the PV present in the oyster gut and oyster faeces is noninfectious, while in contrast, most of the HAV detected in the oyster gut are infectious. Depuration experiments identified a large drop in the count of PV in the gut over a 23-h cleansing period, whereas the levels of HAV and NoV did not significantly decrease.

CONCLUSIONS

Human enterically transmitted viruses are eliminated and inactivated at different rates by Pacific oysters.

SIGNIFICANCE AND IMPACT OF STUDY

The research presented in this article has implications for risk management techniques that are used to improve the removal of infectious human enteric viruses from bivalve molluscs.

Prevalence and potential pathogenicity of Vibrio parahaemolyticus in Chinese mitten crabs (Eriocheir sinensis) harvested from the River Thames estuary, England

Chinese mitten crabs (Eriocheir sinensis) have been described as an alien invasive species in the River Thames, United Kingdom, and elsewhere in Europe. The crabs can cause considerable physical damage to the riverbeds and threaten native ecosystems. Trapping has been considered an option, but such attempts to control mitten crab populations in Germany in the 1930s failed. In the United Kingdom, it has been suggested that commercial exploitation of the species could be employed as a control option. This study was conducted as part of a larger program to assess the suitability of a commercial Chinese mitten crab fishery in the River Thames. Crabs and water samples from the River Thames between 2003 and 2006 were examined for the human pathogenic bacterium Vibrio parahaemolyticus. All samples throughout this testing period were positive for V. parahaemolyticus. The putative pathogenicity markers, thermostable direct hemolysin and thermostable direct-related hemolysin, were detected in one sample, indicating that the crabs possessed the potential to cause V. parahaemolyticus-associated illness if consumed without further processing. Levels of V. parahaemolyticus were higher during the summer than in the winter. This is the first study of V. parahaemolyticus prevalence in European-adapted Chinese mitten crabs.

Viral contaminants of molluscan shellfish: detection and characterisation

Environmental virology started with the detection of poliovirus in water. Since then other enteric viruses responsible for gastroenteritis and hepatitis have replaced enteroviruses as the main target for detection. Most shellfish-borne viral outbreaks are restricted to norovirus and hepatitis A virus, making them the main targets for bivalve virological analysis. The inclusion of virus analysis in regulatory standards for viruses in molluscan bivalve samples must overcome several shortcomings such as the technical difficulties and high costs of virus monitoring, the lack of harmonised and standardised assays and the challenge posed by the ever-changing nature of viruses. Nowadays methods are available to detect, quantify and characterise viral pathogens in molluscan shellfish to reduce the risks of shellfish-borne virus diseases.

Outbreaks where food workers have been implicated in the spread of foodborne disease. Part 4. Infective doses and pathogen carriage

In this article, the fourth in a series reviewing the role of food workers in foodborne outbreaks, background information on the presence of enteric pathogens in the community, the numbers of organisms required to initiate an infection, and the length of carriage are presented. Although workers have been implicated in outbreaks, they were not always aware of their infections, either because they were in the prodromic phase before symptoms began or because they were asymptomatic carriers. Pathogens of fecal, nose or throat, and skin origin are most likely to be transmitted by the hands, highlighting the need for effective hand hygiene and other barriers to pathogen contamination, such as no bare hand contact with ready-to-eat food. The pathogens most likely to be transmitted by food workers are norovirus, hepatitis A virus, Salmonella, Shigella, and Staphylococcus aureus. However, other pathogens have been implicated in worker-associated outbreaks or have the potential to be implicated. In this study, the likelihood of pathogen involvement in foodborne outbreaks where infected workers have been implicated was examined, based on infectious dose, carriage rate in the community, duration of illness, and length of pathogen excretion. Infectious dose estimates are based on volunteer studies (mostly early experiments) or data from outbreaks. Although there is considerable uncertainty associated with these data, some pathogens appear to be able to infect at doses as low as 1 to 100 units, including viruses, parasites, and some bacteria. Lengthy postsymptomatic shedding periods and excretion by asymptomatic individuals of many enteric pathogens is an important issue for the hygienic management of food workers.

Bioaccumulation, retention, and depuration of enteric viruses by Crassostrea virginica and Crassostrea ariakensis oysters

Crassostrea ariakensis oysters are under review for introduction into the Chesapeake Bay. However, the human health implications of the introduction have not been fully addressed. This study evaluated rates of bioaccumulation, retention, and depuration of viruses by Crassostrea virginica and C. ariakensis when the two oyster species were maintained in separate tanks containing synthetic seawater of various salinities (8, 12, or 20 ppt). Oyster bioaccumulation tanks were seeded with 10(3) PFU/ml of hepatitis A virus (HAV), poliovirus, male-specific bacteriophage (MS2), and murine norovirus 1 (MNV-1) and 10(3) PCR units/ml of human norovirus (NoV). After 24 h, depuration commenced as oysters (n = 255) were placed in pathogen-free seawater under continuous filtration. Oysters (n = 6) were sampled weekly for 1 month from each tank. Viral RNA was recovered using a modified proteinase K, guanidine, and glassmilk method and analyzed by quantitative reverse transcription-PCR. The odds of C. ariakensis oysters harboring NoV, MNV-1, or HAV were statistically greater than the odds of C. virginica oysters harboring the same viruses (MNV-1 odds ratio [OR], 4.5; P = 0.01; NoV OR, 8.4; P < 0.001; HAV OR, 11.4; P < 0.001). Unlike C. virginica, C. ariakensis bioaccumulated and retained NoV, MNV-1, and HAV for 1 month at all salinities. Additionally, the odds of an oyster testing positive for NoV was 25.5 times greater (P < 0.001) when the oyster also tested positive for MNV-1. This research helps assess the threat of C. ariakensis as a vehicle for viral pathogens due to the consumption of raw oysters and validates the role for MNV-1 as a surrogate for NoV.

Determination of norovirus contamination in oysters from two commercial harvesting areas over an extended period, using semiquantitative real-time reverse transcription PCR

The human health risk associated with the consumption of molluscan shellfish grown in sewage-contaminated waters is well established. Noroviruses, which cause gastroenteritis, are the principal agents of shellfish-related illness. Fecal-indicator quality standards based on Escherichia coli are well established in Europe and elsewhere. However, norovirus outbreaks after consumption of shellfish meeting these standards still occur, and the need to improve consumer health protection is well recognized. Alternative approaches proposed include direct monitoring of viral pathogens and the use of alternative indicator organisms capable of providing a better indication of virus risk. This study applies a recently developed TaqMan PCR assay to assess norovirus contamination in shellfish. Comparison was made with E. coli as the existing sanitary standard and a male-specific RNA bacteriophage as a possible alternative. Two commercial pacific oyster (Crassostrea gigas) harvesting areas were monitored over a 31-month period. The results show peaks of norovirus contamination in both areas during winter months, with average levels approximately 17 times higher in oysters sampled October to March than during the remainder of the year, consistent with epidemiological data for the United Kingdom showing oyster-associated illness is confined to winter months. While there was no apparent association with E. coli, an association between levels of norovirus contamination and the male-specific RNA bacteriophage was noted, with average norovirus levels over 40 times higher in samples with male-specific RNA bacteriophage counts of >1,000 PFU/100 g than in samples with <100 PFU/100 g. Overall, these results suggest that norovirus monitoring in shellfish production areas could be an effective strategy for reduction of virus risk.

Transmission events within outbreaks of gastroenteritis determined through analysis of nucleotide sequences of the P2 domain of genogroup II noroviruses

Tracking the spread of noroviruses during outbreaks of gastroenteritis is hampered by the lack of sequence diversity in those regions of the genome chosen for virus detection and characterization. Sequence analysis of regions of the genes encoding the RNA-dependent RNA polymerase and the S domain of the capsid does not provide sufficient discrimination between genotypically related strains of different outbreaks. However, analysis of sequences derived from the region encoding the P2 domain showed 100% similarity among strains from the same outbreak and <100% similarity among strains of different outbreaks. The prolonged nature of some hospital outbreaks, links between hospitals, and the introduction of multiple strains of a single genotype associated with an outbreak aboard a cruise ship were determined using this method. This provides a powerful tool for tracking outbreak strains and the subsequent analysis and validation of interventions in a background of multiple introductions of virus strains of the same genotype or genetic cluster.

Epidemiological and virological characterization of a large community-wide outbreak of hepatitis A in southern Italy

A large outbreak of hepatitis A virus (HAV) infection occurred in 2004 in Campania, a region of southern Italy, with 882 cases reported between 1 January and 1 August. The local public health authorities and the Italian National Institute of Health carried out investigations in order to characterize the agent, identify the source of infection and the route of transmission, and implement appropriate control measures. A web-based reporting system enhanced the flow of information between public health authorities, providing real-time epidemic curves and frequency distributions. The same 1B HAV genotype was found in 90% of sera from a subset of patients with acute disease, suggesting a local common source. A case-control study in the municipality with the highest attack rate showed that raw seafood consumption, in particular if illegally sold in water, was strongly associated with HAV illness. Samples of seafood systematically collected from retailers were found contaminated by HAV.

Persistence of caliciviruses in artificially contaminated oysters during depuration

The fate of calicivirus in oysters in a 10-day depuration was assessed. The norovirus gene was persistently detected from artificially contaminated oysters during the depuration, whereas feline calicivirus in oysters was promptly eliminated. The prolonged observation of norovirus in oysters implies the existence of a selective retention mechanism for norovirus within oysters.