Acute gastroenteritis is a common ailment in humans and remains a major public health concern worldwide. Norovirus, a member of the genus Norovirus, in the family Caliciviridae, is considered to be a common cause of outbreaks and sporadic cases of acute gastroenteritis among all age groups.
Reservoir:
- gastrointestinal tract of humans
- capable of surviving in the environment
Epidemiology:
- commonest cause of gastroenteritis in England and Wales
- increased prevalence during colder months
- persons of all ages are at risk from infection. The elderly and very young are at greater risk of developing dehydration
- most people with Norovirus do not access health care services. Outbreaks are very common in semi-closed environments such as schools, hospitals and nursing homes.
Transmission occurs by ingestion of contaminated food or water, exposure to contaminants (fomites, aerosolized vomitus), and person-to-person contact.
- known to have high transmissibility and a low infectious dose, Norovirus has been recognized as the primary source of outbreaks in a range of environments, including nursing homes, hospitals, schools, hotels, and cruise ships
Incubation period:
- usually 12-62 hours, rarely 6-84 hours
Noroviruses can be divided into five genogroups based on the genome sequence of the RNA-dependent RNA polymerase and the capsid regions
- of the five identified genogroups, three distinct strains (GI, GII, and GIV) have been associated with human gastroenteritis,
Clinical features:
- symptoms of a norovirus usually start between 24-48 hours after the initial infection, although they can start after as little as 12 hours. The first symptom is usually a sudden onset of nausea, which is followed by projectile vomiting and watery diarrhoea
- some people may also have:
- a mild fever
- headaches
- abdominal cramps, or
- myalgia
- in rare cases of the norovirus, seizures can occur
- symptoms normally last between 12-60 hours, although most people make a full recovery within one to two days. However, the diarrhoea may last slightly longer
Infectivity:
- whilst symptomatic and for 48-72 hours after diarrhoea has stopped.
Management:
- no specific treatment
- ensure adequate fluid intake; paracetamol if fever or headaches
Notes:
- the ease of person-to-person transmission, low infectious dose and ability to survive in the environment for several days all contribute to the high number of outbreaks caused by Norovirus
- immunity is short-lived; infection with one strain of Norovirus is not protective against other strains.
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