How long is the incubation period for stomach flu

As viral gastro is very infectious, people with symptoms should not go to work or attend child care centres, kindergartens or schools until 48 hours after symptoms have stopped. 

Infectious agents of viral gastroenteritis (not rotavirus)

Small round structured viruses (SRSVs), including noroviruses and other caliciviruses, astroviruses and adenoviruses, are the most common agents.

Clinical features

Illness is characterised by acute onset of symptoms, including fever, myalgias, headache, nausea, vomiting, abdominal cramps and watery diarrhoea, lasting 12–60 hours. Vomiting is relatively more prevalent among children. Viral gastroenteritis is generally self-limiting; however, severe morbidity and rarely mortality may result from dehydration and electrolyte imbalance in people with underlying health conditions. Treatment is supportive.

Abrupt onset of symptoms, forceful vomiting as a prominent symptom and high secondary attack rate in an outbreak of gastroenteritis are features suggestive of norovirus.

Diagnosis

Diagnosis is predominantly based on clinical presentation. Virus in stool can be visualised and distinguished by electron microscopy. Nucleic acid hybridisation and reverse transcriptase polymerase chain reaction assays to detect norovirus genome are sensitive and specific tools for outbreak investigation. Nucleotide sequencing provides a classification of the viruses and is an important tool in establishing vehicles of infection in outbreak settings.

Incubation period of gastroenteritis viruses (not rotavirus)

The incubation period is usually 24–48 hours. The known range for norovirus is 18–72 hours.

Public health significance and occurrence of viral gastroenteritis (not rotavirus)

The endemic burden of viral gastroenteritis is not known; however, approximately 80 per cent of gastroenteritis outbreaks investigated each year in Victoria are attributed to viral pathogens. High secondary attack rates result in outbreaks that are often prolonged and difficult to contain. Norovirus is recognised as the major cause of outbreaks of non-bacterial infectious gastroenteritis. Explosive outbreaks have occurred in institutions, camps, childcare centres, cruise ships, restaurants and following catered functions.

Disease occurs in all age groups and predominantly affects infants and young children; in older children and adults, norovirus is a major pathogen. In Australia, viruses can be detected throughout the year, but are more common from late winter to early summer.

Reservoir of gastroenteritis viruses (not rotavirus)

Humans are the main reservoir.

Mode of transmission of gastroenteritis viruses (not rotavirus)

Viral gastroenteritis is predominantly spread via the faecal-oral route. Transmission is facilitated through contaminated food, water (including ice) and person-to-person contact. Aerosolised vomit is thought to be important in the transmission of norovirus, and virus may persist on contaminated surfaces, such as carpet, for weeks.

Period of communicability of viral gastroenteritis (not rotavirus)

Communicability continues during the acute phase and for as long as viral shedding persists. Cases should be considered infectious until at least 24–48 hours after diarrhoea has ceased. Shedding of norovirus in the absence of clinical illness can persist for up to 2 weeks and is of concern because it can be spread by people handling food

Susceptibility and resistance to viral gastroenteritis (not rotavirus)

Everyone is susceptible to viral gastroenteritis, and infection is not known to confer lifelong immunity.

Control measures for viral gastroenteritis (not rotavirus)

Preventive measures

Prevention depends on good food and personal hygiene, particularly hand washing.

Control of case

Treatment is symptomatic and should focus on maintaining hydration.

Advise the patient to maintain strict personal hygiene and hand washing in the home, and to avoid preparing food for others. Healthcare workers and food handlers should be excluded from work, and children from childcare and school, until at least 48 hours after vomiting and diarrhoea have ceased. Residents of institutions should be isolated until diarrhoea has ceased.

Determine if others are ill. If so, notify the department so that outbreak investigation and control can occur. Provide advice about strict personal, food and home hygiene.

Control of environment

The ability of norovirus to survive relatively high levels of chlorine and varying temperatures (from freezing to 60 °C) means rigorous attention to clean-up procedures and personal and home hygiene is essential in preventing further transmission.

Outbreak measures for viral gastroenteritis (not rotavirus)

An outbreak is defined as two or more related cases of gastroenteritis. The primary aim is to prevent further disease by identifying the source, cleaning contaminated environments and isolating cases.

Special settings

Specific protocols for the management of outbreaks in special settings are available from the department’s Communicable Diseases Section.

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