Norovirus (NoV) is the leading cause of gastroenteritis outbreaks worldwide, and is commonly associated with shellfish. Between 2001-2010 seventeen Australian cases of suspected shellfish related NoV outbreaks were reported in OzFoodNet (Knope, 2011). More recently (March 2013) 400 people were reportedly affected by NoV following consumption of contaminated oysters from Tasmania.
Virus contamination in food poses major concerns for consumers and can impact export trade. The WHO/FAO working group (2008) on food-borne viruses, and European Food Safety Authority’s (EFSA) opinion (2011) ranked bivalves among the highest risk food groups in terms of NoV and hepatitis A virus (HAV). In 2011 the Codex Committee on Food Hygiene ratified a draft guideline on viruses in foods, with a specific annex on bivalves. It recommends that countries monitor for NoV and HAV in bivalves following high risk pollution events. Additionally, in early 2012 EFSA recommended the introduction of an acceptable NoV limit in oysters and the EU Community Reference Laboratory (2012) recommended an ‘absence’ criterion be applied for HAV in bivalves. Because of these impending international regulations (noting that some importing nations already require NoV testing), the Australian oyster industry members have indicated that they would like a more comprehensive evaluation of the prevalence of viruses in Australian oysters. There is little information on the baseline levels of NoV in Australian oysters. Although, a small pilot survey in oysters was conducted in production areas, more information is needed.
Recent developments made at SARDI in the use of molecular biology techniques for virus detection in foods would enable the occurrence of these viruses in bivalves to be determined through a virus prevalence survey. Similar surveys have been undertaken worldwide, including in the USA, UK, France and China, and might contribute to the development of market access strategies at the international level.

The need for further information to assist with the response to OsHV-1 is universally acknowledged by the aquaculture industry broadly, government agencies charged with biosecurity and aquatic animal health scientists in Australia and internationally.
Access to a standardised, reproducible and transferable laboratory infection model is critical to ongoing research efforts. Such a model provides a precise method of testing the effect of factors which are suspected to influence the outcome of an infectious challenge with OsHV-1 on Pacific oysters. The most promising factor for enabling continuation of Pacific oyster production despite the threat of OsHV-1 infection is the identification of genetic variation in susceptibility to POMS. The demand for efficient progress in selective breeding programmes requires a laboratory infection model which is suitable for screening large numbers of candidate families and provides results which can be reliably interpreted.