Norwalk-like viruses (NLV) commonly cause outbreaks of gastroenteritis in hospitals and can result in major disruption of services. It is considered that contamination of the environment can be a cause of transmission and prolonged or recurring outbreaks. In order to control outbreaks it is important to establish the role of environmental contamination in transmission and the decontamination measures required to prevent this. A review of available evidence is described, showing that despite evidence of environmental contamination with NLV during outbreaks, its presence remains unproven as a cause of prolonged or recurring outbreaks. Evidence suggests that the virus might survive for at least 12 days in carpets and 21-28 days in a dried state at room temperature. NLV has been detected from swabs taken from a variety of sources, including lockers, commodes, toilets, door handles, soft furnishings, frequently handled items and horizontal surfaces below and above 1.5 metres. Expert opinion suggests that carpets should be steam cleaned and curtains should be changed following outbreaks. Hypochlorite 1000 ppm is recommended for disinfecting hard surfaces. Further research of environmental contamination and decontamination activities is required.

Summary Noroviruses are important pathogens in both sporadic cases and outbreaks of gastroenteritis in humans. Noroviruses can affect individuals of all ages in a variety of settings, but are a particularly important cause of gastroenteritis in aged-care facilities. The relationship between clinical symptoms and norovirus excretion and the possible role of asymptomatic carriage of norovirus in the elderly are poorly understood. This study examined symptoms and norovirus excretion in elderly individuals associated with a norovirus outbreak in an aged-care facility. Ten individuals aged 79–94 years were recruited for the study. Nine were symptomatic and one was an asymptomatic contact who subsequently developed gastroenteritis. The 10 participants were interviewed regarding their clinical symptoms between two and six times over a three-week study period. One or more sequential faecal samples were collected from all participants over the same period and tested by reverse transcription-polymerase chain reaction for the presence of norovirus. Norovirus was detected in faecal samples from all 10 study participants and was commonly detected in formed stools. In the nine symptomatic participants, acute symptoms such as diarrhoea and vomiting had largely resolved by the third or fourth day of illness, but non-specific symptoms such as headache, thirst and vertigo could persist for as long as 19 days. Both acute and non-specific symptoms appeared to resolve and recur in some participants. The median excretion time for norovirus was 8.6 days (range 2–15 days) in symptomatic participants (N=5). There was no general relationship between the duration of norovirus excretion and the duration of either acute or non-specific symptoms. A faecal sample collected from the asymptomatic contact the day before gastroenteritis symptoms began was positive for norovirus, demonstrating prodromal excretion of norovirus. The results of this study indicate that infection control guidelines should consider both long-term excretion and prodromal excretion of norovirus, and the possibility that formed stools can contain norovirus. Furthermore, the care of elderly individuals recovering from a norovirus infection should take long-term non-specific clinical symptoms into account.