3.1 National surveillance

In Australia, norovirus infection in individual patients is not notifiable in any state or territory. This means that national statistics are not available for the number of patients infected with norovirus each year. State and territory health departments vary in their requirements and mechanisms for reporting norovirus outbreaks or outbreaks of gastroenteritis and when outbreaks should be investigated.

For specific reporting requirements regarding outbreaks, please check with your state or territory health department.

3.1.1 State and territory surveillance

Although norovirus and viral gastroenteritis are not nationally notifiable diseases some states and territories have their own list of additional notifiable diseases. Norovirus may be notified locally, as some states and territories record one or more of the following conditions that are statutory notifications for their jurisdiction:
  • gastroenteritis in an institution
  • foodborne or waterborne illness in two or more related cases
  • food poisoning
  • gastrointestinal illness cluster.
In states and territories where only foodborne or waterborne illness is notifiable, norovirus outbreaks will not necessarily be reported unless the medical practitioner suspects the source to be contaminated food. It can be very difficult to determine the mode of spread of gastroenteritis without a proper epidemiological investigation, and as a precaution it is advisable to report outbreaks if in doubt.

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Managers of institutions may also report outbreaks to health departments, while seeking advice on infection control issues. It will be at the discretion of the PHU how they wish to proceed with the report or investigation. Other states and territories receive notifications of norovirus outbreaks if the outbreak is in an institution or there is a cluster of gastrointestinal illness. In some jurisdictions public health services are regionalised, meaning that the medical officers, laboratories or hospitals are required to notify the PHU of suspected outbreaks.

3.1.2 Objectives of surveillance

The objectives of surveillance and the level of detail in the information collected are different at state and territory levels. However, there are specific objectives that are relevant to surveillance for gastroenteritis outbreaks possibly due to norovirus and other viral agents. The objectives of surveillance of outbreaks are to:
  • ensure prompt identification and management of outbreaks that will enable rapid implementation of control measures, particularly those with a food- or waterborne route of transmission
  • improve understanding of the epidemiology of gastrointestinal agents such as norovirus
  • monitor the effectiveness of current control measures and to provide an evidence base for public health policy, such as these Guidelines.

3.1.3 Objectives of reporting

A PHU may receive reports of suspected outbreaks of norovirus from individuals and agencies other than those obliged to notify under local public health acts (mandatory reporting requirements which may differ between states and territories). Reports may come from ACF, childcare centres, schools, restaurant patrons, attendees at private and public functions where food is served, passengers on coaches, trains and cruise ships among others. These reports may or may not provide a trigger for a public health
response. However, it is important to establish early if the reported outbreak is due to norovirus and if the mode of transmission is person-to-person or foodborne, as investigation processes may be different. In person-to-person spread, infection control measures are more effective if instituted early [63]. On the other hand, foodborne transmission requires a rapid epidemiological investigation including analytical studies and microbiological testing of suspected food items. Investigations and management of the outbreak may depend on the resources available within a PHU.

3.2 National data collection and reporting

OzFoodNet - an initiative of the Australian Government—was established in 2000 to determine the burden and causes of foodborne disease in Australia [64]. OzFoodNet collects and summarises national data on the causes of outbreaks of foodborne illness and gastroenteritis, including those caused by viral agents. Data are available on outbreaks of norovirus transmitted by food, water and infected persons. These data are collated and reported quarterly and an annual report is published in the national journal Communicable Diseases Intelligence [4]. These data are the most comprehensive that exist on norovirus outbreaks in Australia. It is important to interpret outbreak data with caution, as norovirus is not notifiable and changes in reporting may bias results over time. This can make assessment of trends difficult and data may change over time as new information about outbreaks is reported [65].

As mentioned in section 2.2, each year in Australia there are an estimated 1.8 million cases of norovirus infection, making it the
most common cause of gastroenteritis [28].