Norovirus Infection

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Norovirus Infection
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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

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Bacteria
Viruses
Infective
Parasites
Diarrhoea
Non-infective
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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.
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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 III most of human outbreaks.
• Genotype GII.4 main cause of outbreaks since
  2002.

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Norovirus

• Infected patients can shed billions of virus
  particles
• Infectious dose of 10-100 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)

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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.

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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
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Outbreak ManagementCase Definition

• Diarrhoea 3 or more loose stools over 24/24
  period
• Vomiting 2 or more episodes over 24/24 period
• Ds Vs 1 or more episodes over 24/24 period
• (Exclude longstanding diarrhoea)
• (Exclude other causes)
•  

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Clinical Features

• Diarrhoea 85
• Nausea 81
• Abdominal cramps 72
• Vomiting 54
• Low grade fever 51
• Also joint pain, headache, rigors common
• 30 asymptomatic infection

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Laboratory Testing

• Culture.
• 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.

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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.

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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.

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Useful Resources on Norovirus

• http//www.cdc.gov/norovirus/hcp/index.html