1. Norovirus Infection

2. Norovirus- Terminology
Also known as (amongst other things)
Winter vomiting virus
Small Round Structured Virus
Norwalk virus
Belongs to the Calicivirus family (Sapovirus, another virus belonging to the Calicivirus family, can also cause gastroenteritis)
Single stranded non-enveloped RNA virus

3. Bacteria
Viruses
Infective
Parasites
Diarrhoea
Non-infective

4. Main Causes of Viral Gastroenteritis
ROTAVIRUS
Most common cause of severe diarrhoea in childhood, but not uncommon in adult populations. Endemic
ENTERIC ADENOVIRUS
Rotavirus-like childhood diarrhoea, endemic
NOROVIRUS
Causes most outbreaks of gastroenteritis, epidemic in all age groups
ASTROVIRUS
Endemic diarrhoea in young children, some outbreaks.

5. Norovirus Epidemiology
Affects all age groups
Patients with Blood group O most severely affected.
6 main genogroups (I-VI). I, II and IV can affect humans.
Genogroups I&II most of human outbreaks.
Genotype GII.4 main cause of outbreaks since 2002.

6. Norovirus Infected patients can shed billions of virus particles
Infectious dose of virus particles
24-48 hour incubation period
6-60 hour duration of illness
A “mild” and short-lived illness
Viral shedding of 2 weeks or more (However risk of transmission is likely to drop dramatically once symptoms settle)

7. Transmission of Norovirus
Faecal oral
Large droplet spread via aerosolised vomit
Contaminated water
Fomites
Environmentally hardy
Withstands heating to 60oc, freezing and chlorine concentrations up to 10 parts per million
Best disinfectant for cleaning is household bleach (sodium hypochlorite) at 1 in 1000 dilution.

8. “A suspected outbreak”
2 or more patients with gastro-enteritis symptoms that are linked epidemiologically and with no other obvious cause for their symptoms.
Factors making you think of Norovirus
Vomiting
Staff affected
Short duration of symptoms
New Cases
Inform the ICN and Public Health promptly

9. Outbreak Management Case Definition
Diarrhoea – 3 or more loose stools over 24/24 period
Vomiting – 2 or more episodes over 24/24 period
D’s & V’s – 1 or more episodes over 24/24 period
(Exclude longstanding diarrhoea)
(Exclude other causes)

10. Clinical Features Diarrhoea 85% Nausea 81% Abdominal cramps 72%
Vomiting 54%
Low grade fever 51%
Also joint pain, headache, rigors common
30% “asymptomatic infection”
Vomiting more common in young
Diarrhoea more common in elderly

11. Laboratory Testing Culture. Electron Microscopy Enzyme Immunoassay PCR
Not feasible
Electron Microscopy
Catch-all
Not practical for routine lab, slow, labour intensive
Enzyme Immunoassay
Poor sensitivity 50-60%
PCR
Current test, reasonably sensitive(80-90%), expensive
Exclude bacteria, rotavirus, parasites and C.diff as cause of the outbreak.
Typing can be considered if necessary to link individual cases.

12. Laboratory Testing- Norovirus
One stool per patient.
Vomitus can be tested but less sensitive.
Stop testing when Norovirus has been confirmed in a particular ward/area.

13. Nursing during a Norovirus Outbreak
Communication
Hand Hygiene between patients is essential.
Use of PPE (Personal Protective Equipment)
Investigations should be “urgent only” particularly for symptomatic cases.
Patient transfers to other wards should be restricted.
Minimise the number of nurses looking after patients on an affected ward.
If you contract Norovirus, then you should be asymptomatic for two days before returning to work.
Restrictions on visiting.

14. Useful Resources on Norovirus