What is Norovirus?

Norovirus is a highly contagious viral infection. Norovirus is the leading cause of viral gastroenteritis worldwide and is a common cause of outbreaks in residential aged care facilities. Aged care facilities are considered high risk environments for the spread of norovirus, largely due to the close proximity and communal living environments in which residents live, the multiple comorbidities that put the elderly at risk, and factors such as incontinence and dementia which makes isolation challenging.

Prompt interventions are therefore important in any outbreak of  diarrhoea & vomiting.


Signs and Symptoms

Norovirus presents with an acute onset of diarrhoea, abdominal cramps, nausea and vomiting.

There are often systemic symptoms present such as fever, headache, myalgia, malaise and abdominal pain.

Symptoms generally appear 10 to 50 hours after contact with the virus, and the duration of illness normally lasts from 12 to 72 hours

Norovirus is a self-limiting infection.

Definition of a case of Gastroenteritis

  1. Three or more liquid or watery stools above what is normal for the client within a 24 hour period


  1. Two or more episodes of vomiting in 24 hours;


  1. Both of the following: a) A stool culture that is positive for a pathogen causing gastroenteritis (for example Salmonella, Shigella, E coli, Campylobacter, Clostridium difficile) and b) At least 1 sign or symptom compatible with gastroenteritis, (nausea, vomiting, abdominal pain, tenderness, diarrhoea)

Outbreak definition

it is defined as ‘two or more cases of illness linked to a common source’ (ESR 2002). An outbreak of norovirus should be suspected where one patient or resident has signs of gastroenteritis.

A really good rule of thumb is one case is an alert. So if you have one resident with vomiting and diarrhoea, that resident should be isolated and staff should be vigilant for more cases

Residents are isolated from the onset of symptoms until 48 to 72 hours after the last episode of vomiting and diarrhoea

Transmission (how is it spread)?

Norovirus is highly infectious and can be spread in the following ways:

  • by person-to-person contact via the faecal oral route
  • by airborne spread. (When a person vomits, large amounts of virus particles are aerosolised and can be passed on to other people in the same room)
  • by swallowing contaminated food or drink.

This is an excerpt from the the monthly update that is sent out to members of Infection Control NZ. To become a member and receive the full article please contact me at

Have a wonderful day


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