An outbreak of hepatitis A associated with green onions

A simple method to screen cilantro and parsley for fecal indicator viruses

A protocol has been developed to process cilantro and parsley samples for male-specific coliphages. Coliphage recovery depended on the duration of peptone rinsing, and whether the products were intact or cut. After 60 min of rinsing with 0.1% peptone, 78% of spiked coliphages were recovered from intact cilantro samples, and 60% of the spiked coliphages were recovered from cut cilantro samples. The protocol was field tested on a limited scale using cilantro and parsley samples from six retail outlets using enrichment-based and quantitative coliphage assays. Of the 18 retail cilantro and parsley samples that were analyzed, 50% (9 of 18) of the cilantro samples were positive for male-specific coliphages using the enrichment-based assay compared to 39% (7 of 18) of the parsley samples. Using the quantitative coliphage assay, only 28% (5 of 18) of the cilantro samples were positive, and none of the parsley samples were positive. The number of male-specific coliphages ranged between 1 and 11 plaque-forming units per 10 g of cilantro samples. None of the samples was positive for Escherichia coli. The results suggest that simplified male-specific coliphage screening of herb samples is possible and that male-specific coliphages be used along with conventional bacteriological indicators to screen produce for presence of fecal contamination.

Genetic analysis of HAV strains recovered from patients with acute hepatitis from Southern Italy

Southern Italy is an endemic area for HAV infection contributing to the majority of Italian hepatitis A cases. Using molecular analysis, HAV strains have been classified in distinct genotypes and subgenotypes. To characterize HAV wild-type strains circulating in Southern Italy, sequence analysis of VP3-VP1 and VP1/2A junction regions of HAV isolates recovered from 25 patients with acute hepatitis during 2000 and 2001 was carried out. HAV isolates showed a degree of identity, after pairwise comparison with one another, ranging from 91.9-100% in the VP3-VP1 junction region and 89.9-100% in the VP1/2A junction region. All strains belonged to genotype I, with 84% (21/25) of samples clustering in subgenotype IA and 16% (4/25) in subgenotype IB. Cocirculation of subgenotypes IA and IB was observed among isolates from 2000, whereas all strains from 2001 were subgenotype IA. In addition, the subgenotype IA strains formed different clusters, one of which was related closely to some Cuban strains, showing a percent similarity of 98.8% in the 168-base pair segment encompassing the VP1/2A junction and the same amino acid substitution. The latter finding suggests that this subgenotype variant circulates also in the Mediterranean area. The results of the phylogenetic analysis confirm the genetic heterogeneity among HAV strains in Western Europe.

The role of vaccine in controlling hepatitis A epidemics

We report the conduct and results of a review of recent literature to describe various types of epidemics and outbreaks in Italy or countries with similar epidemiological profiles and to assess vaccine use in outbreak situations. We identified three scenarios most likely to occur in Italy: outbreaks occurring in small closed communities (nursery or a primary school), outbreaks in communities of limited dimensions (small towns or villages) and open community settings in which epidemics occur at regular intervals (person-to-person transmission). In closed communities we recommend vaccination of family members and school personnel living or working in close proximity to the index case as well as classmates. We also recommend vaccination when there is a proof of secondary transmission within the community. In small open communities we recommend vaccination of more susceptible age groups such as children and adolescents. For large open communities the only practicable alternative strategy is vaccination of close family contacts of acute cases couple with non-immunity boosting control measures.

Cost-effectiveness of hepatitis A vaccination in children, adolescents, and adults

Hepatitis A is a major public health problem in the United States and other developed countries, largely because decreased natural immunity allows for increased susceptibility. To evaluate the cost-effectiveness of routine vaccination of children, adolescents, and certain high-risk adults against hepatitis A, economic analyses of hepatitis A vaccination were identified through searches of MEDLINE, EMBASE, and BIOSIS (February, 1992, to December, 2001) for studies, reviews, editorials, and letters from peer-reviewed journals published in English, French, German, Italian, or Spanish. Experts were also contacted. Articles conforming to accepted standards of quality for health-economic studies were used to compile data on vaccination of children, and results were synthesized in a narrative review. This review of economic analyses of vaccine use in several developed countries shows cost-effectiveness comparable with that of other vaccines in children and within accepted boundaries for adolescents and high-risk adults.

Modified concentration method for the detection of enteric viruses on fruits and vegetables by reverse transcriptase-polymerase chain reaction or cell culture

Fruits and vegetables may act as a vehicle of human enteric virus if they are irrigated with sewage-contaminated water or prepared by infected food handlers. An elution-concentration method was modified to efficiently detect, by reverse transcriptase-polymerase chain reaction (RT-PCR) or by cell culture, contamination by poliovirus, hepatitis A virus (HAV), and Norwalk-like virus (NLV) of various fresh and frozen berries and fresh vegetables. The protocol included washing the fruit or vegetable surface with 100 mM Tris-HCl, 50 mM glycine, and 3% beef extract, pH 9.5 buffer, which favors viral elution from acid-releasing berries, supplemented with 50 mM MgCl2 to reduce the decrease in viral infectivity during the process. The viral concentration method was based on polyethylene glycol precipitation. Copurified RT-PCR inhibitors and cytotoxic compounds were removed from viral concentrates by chloroform-butanol extraction. Viruses from 100 g of vegetal products could be recovered in volumes of 3 to 5 ml. Viral RNAs were isolated by a spin column method before molecular detection or concentrates were filtered (0.22-microm porosity) and inoculated on cell culture for infectious virus detection. About 15% of infectious poliovirus and 20% of infectious HAV were recovered from frozen raspberry surfaces. The percentage of viral RNA recovery was estimated by RT-PCR to be about 13% for NLV, 17% for HAV, and 45 to 100% for poliovirus. By this method, poliovirus and HAV RNA were detected on products inoculated with a titer of about 5 x 10(1) 50% tissue culture infectious dose per 100 g. NLV RNA was detected at an initial inoculum of 1.2 x 10(3) RT-PCR amplifiable units. This method would be useful for the viral analysis of fruits or vegetables during an epidemiological investigation of foodborne diseases.

Molecular characterization of hepatitis a virus isolates from a transcontinental shellfish-borne outbreak

One hundred eighty-four serologically confirmed cases of hepatitis A were reported in eastern Spain in 1999. A matched case-control study implicated imported coquina clams complying with European Union shellfish standards as the source of infection; this implication was confirmed by the detection by reverse transcription-PCR of hepatitis A virus (HAV) RNA in shellfish samples. In spite of the recognized low variability of HAV, genetic characterization of the complete capsid region of virus isolates from patient serum samples revealed the existence of both synonymous and nonsynonymous variants. Two antigenic variants were detected, one in a discontinuous epitope defined by monoclonal antibody K3-4C8 and a second in a linear VP1 epitope of the virus. In spite of these antigenic variants, all isolates were assigned to genotype IB, providing further evidence that the outbreak originated from a common source, although multiple strains were likely to be involved.

Simultaneous detection and identification of hepatitis A virus and rotavirus by multiplex nucleic acid sequence-based amplification (NASBA) and microtiter plate hybridization system

Human rotavirus and hepatitis A virus (HAV) are two of the most common causes of virus-mediated food-borne illness. Epidemiological investigations of outbreaks associated with these viruses have been hindered by the lack of available methods for their detection in foodstuffs. In this study, a multiplex nucleic acid sequence-based amplification (NASBA) system was developed to detect specifically and simultaneously human rotavirus and HAV. Two sets of primers selected from published nucleic acid sequences were used in the NASBA mixture to amplify viral RNA from both viruses. Denaturing gel electrophoresis revealed two distinct RNA products with 268 and 474 nucleotides amplified from rotavirus and HAV, respectively. The specificity of the multiplex NASBA was confirmed by a microtiter plate hybridization and detection system and by Northern blot analysis using specific oligonucleotide probes. The presence of non-homologous nucleic acid and non-target microorganisms did not have any effect on the specificity of the multiplex NASBA. Using the optimized NASBA and microtiter plate hybridization conditions, as little as 400 PFU ml x (-1) of HAV and 40 PFU ml x (-1) of rotavirus were detected. The multiplex NASBA system offers advantages over monoplex virus detection systems in terms of turnaround time and cost-effectiveness.

Foodborne illness: new developments concerning an old problem

Foodborne illnesses continue to cause substantial morbidity and mortality in the United States, primarily as gastroenteritis but occasionally as other syndromes as well. Most of these illnesses are caused by a variety of widely known infectious agents, principally viruses, and are probably the result of common mistakes in food handling in the home or in restaurants. The epidemiology of foodborne illness is evolving. Major changes in food production, distribution, and consumption have created opportunities for new pathogens to emerge and for old ones to reemerge, and the potential for widespread outbreaks is increasing. Antibiotic resistance in bacterial pathogens resulting from the widespread use of antimicrobial agents in animal husbandry is also an important concern. Clinicians must be aware of the changing epidemiology of foodborne illness to recognize and manage these conditions in the clinical setting. In addition, clinicians are critical in the reporting of recognized or suspected foodborne illness, so that public health authorities are able to investigate, understand, and ultimately better control them. A number of new techniques have been employed, and others under development will improve our ability to recognize and cope with foodborne diseases.

Hepatitis A vaccine

Hepatitis A is an infectious disease frequently reported in the United States. An average of 26,000 cases were reported each year during 1980 to 1999; probably 3 times as many occurred. Hepatitis A vaccines provide a powerful new prevention tool. The 2 inactivated hepatitis A vaccines available as pediatric and adult formulations in the United States and in many other countries are safe, immunogenic, and efficacious. A single dose provides excellent short-term protection; the second dose is thought to be important for long-term protection. Because hepatitis A virus (HAV) is excreted in high concentrations in the stool, the principal mode of transmission is person-to-person by the fecal-oral route, most commonly among household and sexual contacts of people with HAV infection. Children can be important in transmission because they frequently have unrecognized or asymptomatic infection. Implementation of recommendations for routine hepatitis A vaccination of children living in areas with consistently elevated hepatitis A rates appears to be resulting in dramatic declines in the overall incidence of the disease. Improved vaccination coverage and continued monitoring of incidence rates are needed to determine the overall long-term impact of this strategy.

The survival of hepatitis A virus in fresh produce

Fresh produce has been repeatedly implicated as the source of human viral infections, including infection with hepatitis A virus (HAV). The objective of the present study was to evaluate the HAV adsorption capacity of the surface of various fresh vegetables that are generally eaten raw and the persistence of the HAV. To this end, the authors experimentally contaminated samples of lettuce, fennel, and carrot by immersing them in sterile distilled water supplemented with an HAV suspension until reaching a concentration of 5 log tissue culture infectious dose (TCID50)/ml. After contamination, the samples were stored at 4 degrees C and analysed at 0, 2, 4, 7, and 9 days. To detect the HAV, RT-nested-PCR was used; positive samples were subjected to the quantitative determination using cell cultures. The three vegetables differed in terms of their adsorption capacity. The highest quantity of virus was consistently detected for lettuce, for which only a slight decrease was observed over time (HAV titre = 4.44 +/- 0.22 log TCID50/ml at day 0 vs. 2.46 +/- 0.17 log TCID50/ml at day 9, before washing). The virus remained vital through the last day of storage. For the other two vegetables, a greater decrease was observed, and complete inactivation had occurred at day 4 for carrot and at day 7 for fennel. For all three vegetables, washing does not guarantee a substantial reduction in the viral contamination.