An outbreak of norovirus genogroup II associated with New South Wales oysters.

INTRODUCTION: Currently available antigen tests for norovirus (NoV) have excellent specificity but negative results do not always rule out infection. Real-time reverse transcription polymerase chain reaction (RT-PCR) is a useful method for detecting and genotyping NoV in humans and oysters. An outbreak of NoV associated with oyster consumption in northern New South Wales confirmed the value of real-time RT-PCR where immunochromatography (ICT) tests were negative. METHODS: Eight cases of gastrointestinal illness in northern NSW, clinically suggestive of NoV infection, were associated with consumption of oysters. A joint environmental investigation was conducted by the New South Wales Food Authority and local council. One human sample was collected and tested for NoV using ICT and real-time RT-PCR. Oyster samples were tested for NoV utilising real-time RT-PCR. RESULTS: The patient with a stool sample had NoV genogroup II (GII) confirmed by real-time RT-PCR after testing negative by ICT. Illness in all cases was consistent with NoV with median incubation and duration of 36 and 50.5 hours respectively. All cases consumed oysters that were harvested from the same area. Three oyster samples from the harvest area were also positive for NoV GII. A nearby leaking sewer line was identified as the likely source of the contamination with hydrological studies confirming its potential to contaminate implicated oyster leases. CONCLUSION: This investigation confirmed the value of real-time RT-PCR testing of human specimens where ICT tests are negative and clinical illness is suggestive of NoV infection. NoV real-time RT-PCR and epidemiological evidence effectively linked human infection with oyster contamination to motivate a thorough environmental investigation and appropriate action to mitigate further public health risk.

A structured framework for improving outbreak investigation audits.

BACKGROUND: Outbreak investigation is a core function of public health agencies. Suboptimal outbreak investigation endangers both public health and agency reputations. While audits of clinical medical and nursing practice are conducted as part of continuous quality improvement, public health agencies rarely make systematic use of structured audits to ensure best practice for outbreak responses, and there is limited guidance or policy to guide outbreak audit. METHODS: A framework for prioritising which outbreak investigations to audit, an approach for conducting a successful audit, and a template for audit trigger questions was developed and trialled in four foodborne outbreaks and a respiratory disease outbreak in Australia. RESULTS: The following issues were identified across several structured audits: the need for clear definitions of roles and responsibilities both within and between agencies, improved communication between agencies and with external stakeholders involved in outbreaks, and the need for development of performance standards in outbreak investigations - particularly in relation to timeliness of response. Participants considered the audit process and methodology to be clear, useful, and non-threatening. Most audits can be conducted within two to three hours, however, some participants felt this limited the scope of the audit. CONCLUSION: The framework was acceptable to participants, provided an opportunity for clarifying perceptions and enhancing partnership approaches, and provided useful recommendations for approaching future outbreaks. Future challenges include incorporating feedback from broader stakeholder groups, for example those of affected cases, institutions and businesses; assessing the quality of a specific audit; developing training for both participants and facilitators; and building a central capacity to support jurisdictions embarking on an audit. The incorporation of measurable performance criteria or sharing of benchmark performance criteria will assist in the standardisation of outbreak investigation audit and further quality improvement.

Estimate of the number of Campylobacter infections in the Hunter region, NSW, 2004-2007.

OBJECTIVES: Campylobacteriosis is not notifiable in NSW and the number of cases of Campylobacter disease is thus not well described. METHODS: De-identified campylobacteriosis records for 2004-2007 were requested from laboratories in the Hunter region of NSW. Based on notifying laboratory, a Salmonella notification weighting was applied to laboratory-confirmed campylobacteriosis cases to provide an overall estimate of Campylobacter disease in the area. RESULTS: The estimated median of the annual number of laboratory-confirmed campylobacteriosis cases was 788 (range 700-1022). The ratio of estimated Campylobacter cases to Salmonella notifications was 5.5 : 1. CONCLUSION: Campylobacter infection causes considerable disease in the Hunter, and likely in NSW. Regular review of Campylobacter laboratory results may be valuable.

A norovirus outbreak associated with consumption of NSW oysters: implications for quality assurance systems.

Norovirus is a common cause of gastroenteritis outbreaks associated with raw shellfish consumption. In Australia there have been several reports of norovirus outbreaks associated with oysters despite the application of regulatory measures recommended by Food Standards Australia New Zealand. This study describes an outbreak of norovirus gastroenteritis following the consumption of New South Wales oysters. In September 2007, OzFoodNet conducted a cohort study of a gastroenteritis outbreak amongst people that had dined at a Port Macquarie restaurant. Illness was strongly associated with oyster consumption, with all cases having eaten oysters from the same lease (RR undefined, p < 0.0001). Norovirus was detected in a faecal specimen. Although no pathogen was identified during the environmental investigation, the source oyster lease had been closed just prior to harvesting due to sewage contamination. Australian quality assurance programs do not routinely test oysters for viral contamination that pose a risk to human health. It is recommended that the feasibility of testing oysters for norovirus, particularly after known faecal contamination of oyster leases, be assessed.

A multi-jurisdictional outbreak of hepatitis A related to a youth camp--implications for catering operations and mass gatherings.

In June 2003, Australian state and territory health departments were notified of an outbreak of Hepatitis A in people who had attended a five-day youth camp. Approximately 350 people attended the event in Central Australia between 24 and 28 April 2003. The public health investigation comprised of case identification, food handler interviews, an environmental health investigation of the campground and associated food premises, laboratory analysis of blood specimens and food/water samples, and an epidemiological study. Twenty-one cases fitted the case definition for the outbreak. A retrospective cohort study involving four states was conducted, with 213 people interviewed. Coleslaw and cordial were significantly associated with illness, however when the two exposures were adjusted for each other to account for confounding, only coleslaw remained significantly associated with illness (adjusted RR 2.5, 95% CI 1.09 - 5.77). The investigation highlighted a number of food hygiene and safety issues relating to the catering of mass gatherings. Implementation of food safety programs in these settings are likely to reduce the occurrence of such outbreaks. The recent proposal by Food Standards Australia New Zealand to mandate food safety programs for catering operations is supported.