Rotavirus virus-like particles as surrogates in environmental persistence and inactivation studies

The UV Dose Used for Disinfection of Drinking Water in Sweden Inadequately Inactivates Enteric Virus with Double-Stranded Genomes

Irradiation with ultraviolet light (UV) at 254 nm is effective in inactivating a wide range of human pathogens. In Sweden, a UV dose of 400 J/m² is often used for the treatment of drinking water. To investigate its effect on virus inactivation, enteric viruses with different genomic organizations were irradiated with three UV doses (400, 600, and 1000 J/m²), after which their viability on cell cultures was examined. Adenovirus type 2 (double-stranded DNA), simian rotavirus 11 (double-stranded RNA), and echovirus 30 (single-stranded RNA) were suspended in tap water and pumped into a laboratory-scale Aquada 1 UV reactor. Echovirus 30 was reduced by 3.6-log₁₀ by a UV dose of 400 J/m². Simian rotavirus 11 and adenovirus type 2 were more UV resistant with only 1-log₁₀ reduction at 400 J/m² and needed 600 J/m² for 2.9-log₁₀ and 3.1-log₁₀ reductions, respectively. There was no significant increase in the reduction of viral viability at higher UV doses, which may indicate the presence of UV-resistant viruses. These results show that higher UV doses than those usually used in Swedish drinking water treatment plants should be considered in combination with other barriers to disinfect the water when there is a risk of fecal contamination of the water.

Epidemiological significance of the occurrence and persistence of rotaviruses in water and sewage: a critical review and proposal for routine microbiological monitoring

Globally, waterborne gastroenteritis attributable to rotaviruses is on the increase due to the rapid increase in population growth, poor socioeconomic conditions, and drastic changes in climatic conditions. The burden of diarrhea is quite alarming in developing nations where the majority of the populations still rely on untreated surface water that is usually polluted for their immediate water needs. Humans and animals of all ages are affected by rotaviruses. In humans, the preponderance of cases occurs in children under 5 years. Global efforts in advancing water/wastewater treatment technologies have not yet realized the objective of complete viral removal from wastewater. Most times, surface waters are impacted heavily by inadequately treated wastewater run-offs thereby exposing people or animals to preventable health risks. The relative stability of rotaviruses in aquatic matrices during wastewater treatment, poor correlation of bacteriological indicators with the presence of rotaviruses, and their infectiousness at a low dose informed the proposal for inclusion in the routine microbiological water screening panel. Environmental monitoring data have been shown to provide early warnings that can complement clinical data used to monitor the impact of current rotavirus vaccination in a community. This review was therefore undertaken to critically appraise rotavirus excretion and emission pathways, and the existence, viability and persistence in the receiving aquatic milieu. The efficiency of the current wastewater treatment modality for rotavirus removal, correlation of the current bacteriological water quality assessment strategy, public health risks and current laboratory methods for an epidemiological study were also discussed.

Sensitivity of Bacteria, Protozoa, Viruses, and Other Microorganisms to Ultraviolet Radiation

Data concerning the sensitivity of various organisms to ultraviolet (UV) radiation exposure are very important in the design of UV disinfection equipment. This review analyzes fluence data from almost 250 studies and organizes the data into a set of recommended fluence values for specific log reductions and an appendix containing all the collected data. This article was sponsored by Dianne L. Poster, Material Measurement Laboratory, and C. Cameron Miller, Physical Measurement Laboratory, National Institute of Standards and Technology (NIST). It is published in collaboration with the International Ultraviolet Association as a complement to the NIST Workshop on Ultraviolet Disinfection Technologies, 14-15 January 2020, Gaithersburg, MD. The views expressed represent those of the authors and not necessarily those of NIST.

Predictive Water Virology: Hierarchical Bayesian Modeling for Estimating Virus Inactivation Curve

Hazard analysis and critical control point (HACCP) are a series of actions to be taken to ensure product consumption safety. In food poisoning risk management, researchers in the field of predictive microbiology calculate the values that provide minimum stress (e.g., temperature and contact time in heating) for sufficient microbe inactivation based on mathematical models. HACCP has also been employed for health risk management in sanitation safety planning (SSP), but the application of predictive microbiology to water-related pathogens is difficult because the variety of pathogen types and the complex composition of the wastewater matrix does not allow us to make a simple mathematical model to predict inactivation efficiency. In this study, we performed a systematic review and meta-analysis to construct predictive inactivation curves using free chlorine for enteric viruses based on a hierarchical Bayesian model using parameters such as water quality. Our model considered uncertainty among virus disinfection tests and difference in genotype-dependent sensitivity of a virus to disinfectant. The proposed model makes it possible to identify critical disinfection stress capable of reducing virus concentration that is below the tolerable concentration to ensure human health.

Preparation of quadri-subtype influenza virus-like particles using bovine immunodeficiency virus gag protein

Influenza VLPs comprised of hemagglutinin (HA), neuraminidase (NA), and matrix (M1) proteins have been previously used for immunological and virological studies. Here we demonstrated that influenza VLPs can be made in Sf9 cells by using the bovine immunodeficiency virus gag (Bgag) protein in place of M1. We showed that Bgag can be used to prepare VLPs for several influenza subtypes including H1N1 and H10N8. Furthermore, by using Bgag, we prepared quadri-subtype VLPs, which co-expressed within the VLP the four HA subtypes derived from avian-origin H5N1, H7N9, H9N2 and H10N8 viruses. VLPs showed hemagglutination and neuraminidase activities and reacted with specific antisera. The content and co-localization of each HA subtype within the quadri-subtype VLP were evaluated. Electron microscopy showed that Bgag-based VLPs resembled influenza virions with the diameter of 150-200nm. This is the first report of quadri-subtype design for influenza VLP and the use of Bgag for influenza VLP preparation.

Retention of Rotavirus Infectivity in Mussels Heated by Using the French Recipe Moules Marinières

To evaluate the persistence of infectious virus after heating, mussels contaminated with a rotavirus strain were prepared following the French recipe moules marinières (mariner's mussels). Rotavirus was then quantified by real-time quantitative PCR (RT-qPCR) and a cell culture infectivity assay. Results showed the persistence of infectious virus after 3 min of cooking. After 5 min, when no infectious virus could be detected, the RT-qPCR approach showed a 1-log decrease compared with concentrations detected after 1 min of cooking.

Thermal Inactivation of Foodborne Enteric Viruses and Their Viral Surrogates in Foods

Foodborne viruses, in particular human norovirus and hepatitis A virus, are the most common causes of food-associated infections and foodborne illness outbreaks around the world. Since it is currently not possible to cultivate human noroviruses and the wild-type strain of hepatitis A virus in vitro, the use of a variety of viral surrogates is essential to determine appropriate thermal processing conditions to reduce the risk associated with their contamination of food. Therefore, the objectives of this review are to (i) present pertinent characteristics of enteric foodborne viruses and their viral surrogates, (ii) discuss the viral surrogates currently used in thermal inactivation studies and their significance and value, (iii) summarize available data on thermal inactivation kinetics of enteric viruses, (iv) discuss factors affecting the efficacy of thermal treatment, (v) discuss suggested mechanisms of thermal inactivation, and (vi) provide insights on foodborne enteric viruses and viral surrogates for future studies and industrial applications. The overall goal of this review is to contribute to the development of appropriate thermal processing protocols to ensure safe food for human consumption.

Virus Sensitivity Index of UV disinfection

A new concept of Virus Sensitivity Index (VSI) is defined as the ratio between the first-order inactivation rate constant of a virus, ki, and that of MS2-phage during UV disinfection, kr. MS2-phage is chosen as the reference virus because it is recommended as a virus indicator during UV reactor design and validation by the US Environmental Protection Agency. VSI has wide applications in research, design, and validation of UV disinfection systems. For example, it can be used to rank the UV disinfection sensitivity of viruses in reference to MS2-phage. There are four major steps in deriving the equation between Hi/Hr and 1/VSI. First, the first-order inactivation rate constants are determined by regression analysis between Log I and fluence required. Second, the inactivation rate constants of MS2-phage are statistically analysed at 3, 4, 5, and 6 Log I levels. Third, different VSI values are obtained from the ki of different viruses dividing by the kr of MS2-phage. Fourth, correlation between Hi/Hr and 1/VSI is analysed by using linear, quadratic, and cubic models. As expected from the theoretical analysis, a linear relationship adequately correlates Hi/Hr and 1/VSI without an intercept. VSI is used to quantitatively predict the UV fluence required for any virus at any log inactivation (Log I). Four equations were developed at 3, 4, 5, and 6 Log I. These equations have been validated using external data which are not used for the virus development. At Log I less than 3, the equation tends to under-predict the required fluence at both low Log I such as 1 and 2 Log I. At Log I greater than 3 Log I, the equation tends to over-predict the fluence required. The reasons for these may very likely be due to the shoulder at the beginning and the tailing at the end of the collimated beam test experiments. At 3 Log I, the error percentage is less than 6%. The VSI is also used to predict inactivation rate constants under two different UV disinfection scenarios such as under sunlight and different virus aggregates. The correlation analysis shows that viruses will be about 40% more sensitive to sunlight than to UV254. On the other hand, virus size of 500 nm will reduce their VSI by 10%. This is the first attempt to use VSI to predict the required fluence at any given Log I. The equation can be used to quantitatively evaluate other parameters influencing UV disinfection. These factors include environmental species, antibiotic-resistant bacteria or genes, photo and dark repair, water quality such as suspended solids, and UV transmittance.

Flagellin in fusion with human rotavirus structural proteins exerts an adjuvant effect when delivered with replicating but non-disseminating adenovectors through the intrarectal route

Human rotavirus (HRV) is the worldwide leading cause of gastroenteritis in young children. Two live attenuated HRV vaccines have been approved since 2006. However, these live vaccines still have potential risks including reversion of virulence. Adenoviruses are suitable vectors for mucosal administration of subunit vaccines. In addition to the adjuvant effect of certain adenovirus components, the use of an adjuvant like flagellin is also another means to increase the immune response to the immunogen. The aim of this study was to determine whether flagellin in fusion with HRV structural proteins stimulates the innate immune response and enhances the HRV-specific immune response when delivered through the intrarectal route with replicating but non-disseminating adenovector (R-AdV). Salmonella typhimurium flagellin B (FljB) in fusion with HRV VP4Δ::VP7 protein induced IL-1β production in J774A.1 macrophages exposed to the R-AdV. Intrarectal administration of R-AdVs expressing either VP4Δ::VP7 or VP4Δ::VP7::FljB in BALB/c mice resulted in HRV-specific mixed Th1/Th2 immune responses. The HRV-specific antibody response elicited with the use of R-AdV expressing VP4Δ::VP7::FljB was higher than that with R-AdV expressing VP4Δ::VP7. The results also show that the replication capability of R-AdVs contributed to enhance the HRV-specific immune response as compared with that obtained with non-replicative AdVs. This work lays the foundation for using the R-AdV system and FljB-adjuvanted formulation to elicit a mucosal immune response specific to HRV.

Effects of chlorine and chlorine dioxide on human rotavirus infectivity and genome stability

Despite the health risks posed by waterborne human rotavirus (HRV), little information is available concerning the effectiveness of chlorine or chlorine dioxide (ClO2), two common disinfectants of public water sources, against HRV and their effects on its genome remain poorly understood. This study investigated the effects of chlorine and ClO2 on purified HRV by using cell culture and RT-PCR to assess virus infectivity and genetic integrity, respectively. The disinfection efficacy of ClO2 was found to be higher than that of chlorine. According to the efficiency factor Hom model, Ct value (mg/L min) ranges required for a 4-log reduction of HRV at 20 °C by chlorine and ClO2 were 5.55-5.59 and 1.21-2.47 mg/L min, respectively. Detection of the 11 HRV genome segments revealed that damage to the 1227-2354 bp of the VP4 gene was associated with the disappearance of viral infectivity by chlorine. However, no complete accordance between culturing and RT-PCR assays was observed after treatment of HRV with ClO2. These results collectively indicate that the current practice of chlorine disinfection may be inadequate to manage the risk of waterborne HRV infection, and offer the potential to monitor the infectivity of HRV adapting PCR-based protocols in chlorine disinfection.

Expression of human rotavirus chimeric fusion proteins from replicating but non disseminating adenovectors and elicitation of rotavirus-specific immune responses in mice

The aim of this study was to evaluate the usefulness of replicating but non disseminating adenovirus vectors (AdVs) as vaccine vector using human rotavirus (HRV) as a model pathogen. HRV VP7, VP4, or VP4Δ (N-terminal 336 amino acids of VP4) structural proteins as well as the VP4Δ::VP7 chimeric fusion protein were expressed in mammalian cells when delivered with the AdVs. A preliminary experiment demonstrated that VP4Δ was able to induce a HRV-specific IgG response in BALB/c mice inoculated intramuscularly with AdVs expressing the rotaviral protein. Moreover, an AdV-prime/plasmid DNA-boost regimen of vectors resulted in VP4Δ-specific antibody (Ab) titers ~4 times higher than those obtained from mice immunized with AdVs alone. Subsequently, the various HRV protein-encoding AdVs were compared using the AdV-prime/plasmid DNA-boost regimen. Higher IgG and IgA responses to HRV were obtained when VP4Δ::VP7 fusion protein was used as an immunogen as compared to VP7 or VP4 alone or to a mix of both proteins delivered independently by AdVs. A synergetic effect in terms of Ab was obtained with VP4Δ::VP7. In conclusion, this study demonstrated for the first time the suitability of using replicating but non disseminating AdVs as vaccine vector and the VP4Δ::VP7 fusion protein as an immunogen for vaccination against HRV.

Natural persistence of food- and waterborne viruses

This chapter summarises data on the persistence of food-and waterborne viruses in the natural environment and discusses the different factors which can affect this persistence. Conventional and alternative methods by which persistence can be studied are described, and the natural factors influencing virus persistence outside the host organism are discussed. Available data concerning virus persistence in water, soil, on surfaces and in food products are reviewed.

Stability of human enteric viruses in seawater samples from mollusc depuration tanks coupled with ultraviolet irradiation

AIMS

To evaluate the stability in seawater of human adenovirus (HAdV2), murine norovirus (MNV-1) and hepatitis A virus (HAV) in a shellfish depuration system with and without ultraviolet (UV) treatment.

METHODS AND RESULTS

Seawater was seeded with viruses and disinfected using a 36 W lamp. Samples were collected at 24, 48, 72, 96 and 120 h; viruses were concentrated and the viral decay was evaluated using molecular and cell culture methods. Based on the molecular results, at 120 h of disinfection, there was a reduction of more than 3 log(10) for HAdV2 and HAV; MNV-1, a 4.5 log(10) reduction was observed at 72 h. Infectious MNV-1 was not detected after 72 h of treatment; while HAdV2 remained infectious. Seawater not treated demonstrated a progressive viral reduction for the three viruses tested.

CONCLUSIONS

The UV reduced the number of viral particles, and the results indicate there is natural and gradual decrease of viral load and viability in seawater.

SIGNIFICANCE AND IMPACT OF THE STUDY

UV irradiation is the method of choice for shellfish depuration in many countries; this work showed useful information about the viral stability in seawater and application of UV to water disinfection to be used in shellfish depuration tanks.

Temporal dynamics and decay of putatively allochthonous and autochthonous viral genotypes in contrasting freshwater lakes

Aquatic viruses play important roles in the biogeochemistry and ecology of lacustrine ecosystems; however, their composition, dynamics, and interactions with viruses of terrestrial origin are less extensively studied. We used a viral shotgun metagenomic approach to elucidate candidate autochthonous (i.e., produced within the lake) and allochthonous (i.e., washed in from other habitats) viral genotypes for a comparative study of their dynamics in lake waters. Based on shotgun metagenomes prepared from catchment soil and freshwater samples from two contrasting lakes (Cayuga Lake and Fayetteville Green Lake), we selected two putatively autochthonous viral genotypes (phycodnaviruses likely infecting algae and cyanomyoviruses likely infecting picocyanobacteria) and two putatively allochthonous viral genotypes (geminiviruses likely infecting terrestrial plants and circoviruses infecting unknown hosts but common in soil libraries) for analysis by genotype-specific quantitative PCR (TaqMan) applied to DNAs from viruses in the viral size fraction of lake plankton, i.e., 0.2 μm > virus > 0.02 μm. The abundance of autochthonous genotypes largely reflected expected host abundance, while the abundance of allochthonous genotypes corresponded with rainfall and storm events in the respective catchments, suggesting that viruses with these genotypes may have been transported to the lake in runoff. The decay rates of allochthonous and autochthonous genotypes, assessed in incubations where all potential hosts were killed, were generally lower (0.13 to 1.50% h(-1)) than those reported for marine virioplankton but similar to those for freshwater virioplankton. Both allochthonous and autochthonous viral genotypes were detected at higher concentrations in subsurface sediments than at the water-sediment interface. Our data indicate that putatively allochthonous viruses are present in lake plankton and sediments, where their temporal dynamics reflect active transport to the lake during hydrological events and then decay once there.

Label-free chemiresistive immunosensors for viruses

We report development, characterization, and testing of chemiresistive immunosensors based on single polypyrrole (Ppy) nanowire for highly sensitive, specific, label free, and direct detection of viruses. Bacteriophages T7 and MS2 were used as safe models for viruses for demonstration. Ppy nanowires were electrochemically polymerized into alumina template, and single nanowire based devices were assembled on a pair of gold electrodes by ac dielectrophoretic alignment and anchored using maskless electrodeposition. Anti-T7 or anti-MS2 antibodies were immobilized on single Ppy nanowire using EDC-NHS chemistry to fabricate nanobiosensor for the detection of corresponding bacteriophage. The biosensors showed excellent sensitivity with a lower detection limit of 10(-3) plaque forming unit (PFU) in 10 mM phosphate buffer, wide dynamic range and excellent selectivity. The immunosensors were successfully applied for the detection of phages in spiked untreated urban runoff water samples. The results show the potential of these sensors in health care, environmental monitoring, food safety and homeland security for sensitive, specific, rapid, and affordable detection of bioagents/pathogens.

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.

Detection of infectious rotavirus in naturally contaminated source waters for drinking water production

AIMS

To assess public health risks of rotavirus via drinking water consumption, a cell culture-PCR assay was developed and optimized for the detection of infectious environmental rotavirus strains in naturally contaminated source waters for drinking water production.

METHODS AND RESULTS

Infectious rotavirus concentrations were estimated by an optimized cell culture-PCR assay as most probable numbers by using the presence or absence of replicated virus in different sample volumes. Infectious rotavirus was detected in 11 of 12 source water samples in concentrations varying from 0.19 (0.01-0.87) to 8.3 (1.8-34.0) infectious PCR detectable units per litre (IPDU/l), which was not significantly different from the concentrations of infectious enterovirus in these samples.

CONCLUSIONS

In 55% of the samples, rotavirus genomes were 1000 to 10 000 times (3 log(10)-4 log(10)) more abundantly present than infectious rotavirus particles, whereas in the remaining 45% of the samples, rotavirus genomes were less than 1000 times (<3 log(10)) more abundantly present.

SIGNIFICANCE AND IMPACT OF THE STUDY

The broad variation observed in the ratios of rotavirus RNA and infectious particles demonstrates the importance of detecting infectious viruses instead of viral RNA for the purposes involving estimations of public health risks.

Eukaryotic viruses in wastewater samples from the United States

Human fecal matter contains a large number of viruses, and current bacterial indicators used for monitoring water quality do not correlate with the presence of pathogenic viruses. Adenoviruses and enteroviruses have often been used to identify fecal pollution in the environment; however, other viruses shed in fecal matter may more accurately detect fecal pollution. The purpose of this study was to develop a baseline understanding of the types of viruses found in raw sewage. PCR was used to detect adenoviruses, enteroviruses, hepatitis B viruses, herpesviruses, morbilliviruses, noroviruses, papillomaviruses, picobirnaviruses, reoviruses, and rotaviruses in raw sewage collected throughout the United States. Adenoviruses and picobirnaviruses were detected in 100% of raw sewage samples and 25% and 33% of final effluent samples, respectively. Enteroviruses and noroviruses were detected in 75% and 58% of raw sewage samples, respectively, and both viral groups were found in 8% of final effluent samples. This study showed that adenoviruses, enteroviruses, noroviruses, and picobirnaviruses are widespread in raw sewage. Since adenoviruses and picobirnaviruses were detected in 100% of raw sewage samples, they are potential markers of fecal contamination. Additionally, this research uncovered previously unknown sequence diversity in human picobirnaviruses. This baseline understanding of viruses in raw sewage will enable educated decisions to be made regarding the use of different viruses in water quality assessments.

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.

Infectivity and genome persistence of rotavirus and astrovirus in groundwater and surface water

In this work, we have characterized the survival of Rhesus rotavirus (RRV) and human astrovirus Yuc8 in clean groundwater and contaminated surface water, as well as in phosphate-buffered solutions maintained in the same conditions as the environmental waters, and have compared the dynamics of virus inactivation with the persistence of the viral genomes, as determined by quantitative reverse transcriptase-polymerase chain reaction (qRT-PCR). In addition, we also studied the tolerance of these viruses to chlorine disinfection. The reduction of infectivity of astrovirus was higher than for rotavirus, and also higher for both viruses in surface water as compared to groundwater. The enterobacterial content of the water as well as extrinsic factors, such as temperature and light, correlated with the stability of virus infectivity, and with the persistence of the virus genetic material, suggesting that molecular techniques to detect and quantify viral genomes would be suitable for the detection of viruses in water. The virus infectivity persisted in both types of water as well as in chlorine for times longer than previously reported. No decrease of infectivity was observed after 15 days of incubation in either type of water and the viruses remained infectious for months in groundwater. After 120 min in groundwater containing 2 mg/L of free chlorine, the infectivity of rotavirus and astrovirus was reduced by 0.78 and 1.3 logs, respectively. The longer persistence of viruses in this study could result from a combination of factors, including aggregation of the virus.

Norwalk virus-specific binding to oyster digestive tissues

The primary pathogens related to shellfish-borne gastroenteritis outbreaks are noroviruses. These viruses show persistence in oysters, which suggests an active mechanism of virus concentration. We investigated whether Norwalk virus or viruslike particles bind specifically to oyster tissues after bioaccumulation or addition to tissue sections. Since noroviruses attach to carbohydrates of the histo-blood group family, tests using immunohistochemical analysis were performed to evaluate specific binding of virus or viruslike particles to oyster tissues through these ligands. Viral particles bind specifically to digestive ducts (midgut, main and secondary ducts, and tubules) by carbohydrate structures with a terminal N-acetylgalactosamine residue in an alpha linkage (same binding site used for recognition of human histo-blood group antigens). These data show that the oyster can selectively concentrate a human pathogen and that conventional depuration will not eliminate noroviruses from oyster tissue.

Use of rotavirus virus-like particles as surrogates to evaluate virus persistence in shellfish

Rotavirus virus-like particles (VLPs) and MS2 bacteriophages were bioaccumulated in bivalve mollusks to evaluate viral persistence in shellfish during depuration and relaying under natural conditions. Using this nonpathogenic surrogate virus, we were able to demonstrate that about 1 log10 of VLPs was depurated after 1 week in warm seawater (22 degrees C). Phage MS2 was depurated more rapidly (about 2 log10 in 1 week) than were VLPs, as determined using a single-compartment model and linear regression analysis. After being relayed in the estuary under the influence of the tides, VLPs were detected in oysters for up to 82 days following seeding with high levels of VLPs (concentration range between 10(10) and 10(9) particles per g of pancreatic tissue) and for 37 days for lower contamination levels (10(5) particles per g of pancreatic tissue). These data suggest that viral particles may persist in shellfish tissues for several weeks.