1.1 Norovirus

Norovirus is an infectious virus. It is recognised as a leading cause of acute gastroenteritis worldwide, and is the most common cause of outbreaks [1]. Noroviruses are highly infectious and are mainly spread from person to person [2]. In addition, aerosolised vomit can result in widespread environmental contamination and facilitate spread of the disease. These features contribute to widespread and intractable outbreaks in semi-closed environments such as planes [3]. Outbreaks have been reported in a variety of settings including hospitals, cruise ships, schools, prisons and childcare centres. In Australia, norovirus outbreaks are most commonly reported in Aged-care facilities (ACF), healthcare facilities and childcare centres [4]. These outbreaks can have an impact on our economic and social system as well as placing a major burden on the heath system.

1.2 History

In 2002, a surge of gastroenteritis outbreaks on cruise ships, aged care and healthcare facilities in the United States (US) and Europe was attributed to a new virus strain [5]. Australian health authorities also experienced a surge in reported outbreaks, which continues and is recognised as an emerging public health issue. Similarly, in 2006 and 2007, Australia experienced further surges of outbreaks due to new strains of norovirus known as GII.4, which were also reported in other countries [6, 7].

The exact reasons for these global increases in norovirus infections are not well understood. However, it is likely that predominance of these strains is due to the regular genetic shift that occurs in viruses, along with strain-based differences in virulence that can result in the global spread of viruses [8-11].

1.3 Detecting norovirus

The development of Reverse Transcription-Polymerase Chain Reaction (RT-PCR) diagnostic tests in the 1990s has improved the detection of norovirus infection. This has allowed for rapid detection of sporadic cases and outbreaks. Development of sensitive molecular techniques has demonstrated that these viruses are genetically diverse, with new strains frequently replacing predominant ones. Recent improvements in diagnostic techniques have changed the understanding of the clinical significance and epidemiology of this virus. In particular, diagnostic pathology laboratories are now commonly testing for norovirus using Enzyme-Linked Immunosorbent Assay (ELISA) antigen tests

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1.4 Managing norovirus

The virus cannot be cultured in the laboratory, which means that gathering evidence on the effectiveness of control measures has been difficult. It is not clear how long the virus survives in the environment, the infectivity of post-symptomatic shedding or the best use of chemical agents for disinfection.

Most of the guidelines available on norovirus and viral gastroenteritis are written specifically for management of norovirus outbreaks in ACFs, hospitals and cruise ships. Consequently, there is very little information provided specifically for managing outbreaks in other settings such as schools, sporting events and camps. Nevertheless, the principles outlined in Chapter 8 on cleaning and disinfection, handwashing, exclusion of affected people and isolation or cohorting of infected patients are applicable to all settings and should guide decision making in all circumstances.