Quantitative Risk Assessments of Hepatitis A Virus and Hepatitis E Virus from Raw Oyster Consumption.

A quantitative risk assessment of hepatitis A virus (HAV) and hepatitis E virus (HEV) from raw oyster consumption from farm and retail was evaluated over three seasons. This risk assessment comprises four steps: hazard identification, dose-response assessment, exposure assessment, and risk characterization. We used probabilistic models for prevalence, concentration, and oyster consumption. HEV dose-response (DR) model based on HEV dosing in chimpanzees and used to perform a dose-response assessment of HEV was proposed. Both HAV and HEV were simultaneously enumerated by real-time PCR to determine viral doses. The probabilistic prevalences of HAV and HEV were in the ranges of 8-20% and 8-40%, respectively. The best-fit DR model was the beta-Poisson with alpha and N50 equal to 216.9 and 3.03 × 107 , respectively. After running the Monte Carlo simulation, the annual cases of foodborne hepatitis A and hepatitis E from raw oyster consumption from farms were 9,264-17,526 and 1-604, respectively, while those at retail were 7,694-14,591 and 1-204, respectively. This study suggested that consuming farm oysters poses a significantly higher risk of hepatitis A than hepatitis E. The best-fit DR model for HEV developed in this study could determine risks of hepatitis E from raw oyster consumption in Thailand.

An Outbreak of Acute Hepatitis Caused by Genotype IB Hepatitis A Viruses Contaminating the Water Supply in Thailand.

BACKGROUND: In 2000, an outbreak of acute hepatitis A was reported in a province adjacent to Bangkok, Thailand. AIMS: To investigate the cause of the 2000 hepatitis A outbreaks in Thailand using molecular epidemiological analysis. METHODS: Serum and stool specimens were collected from patients who were clinically diagnosed with acute viral hepatitis. Water samples from drinking water and deep-drilled wells were also collected. These specimens were subjected to polymerase chain reaction (PCR) amplification and sequencing of the VP1/2A region of the hepatitis A virus (HAV) genome. The entire genome sequence of one of the fecal specimens was determined and phylogenetically analyzed with those of known HAV sequences. RESULTS AND CONCLUSIONS: Eleven of 24 fecal specimens collected from acute viral hepatitis patients were positive as determined by semi- nested reverse transcription PCR targeting the VP1/2A region of HAV. The nucleotide sequence of these samples had an identical genotype IB sequence, suggesting that the same causative agent was present. The complete nucleotide sequence derived from one of the samples indicated that the Thai genotype IB strain should be classified in a unique phylogenetic cluster. The analysis using an adjusted odds ratio showed that the consumption of groundwater was the most likely risk factor associated with the disease.