Norovirus gastroenteritis

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.

Reference:

• 1) NHS Choices - Norovirus (accessed 9/2/20).
• 2) PHE (2019). Recommendations for the Public Health Management of Gastrointestinal Infections