Norovirus (viral gastroenteritis)

Question 1

Is norovirus a nationally notifiable disease?

Answer 1

No.

Not notifiable in Tasmania either but gastroenteritis outbreaks notifiable.

Question 2

What organism causes norovirus infection?

Answer 2

Norovirus (genus). Also called Norwalk virus (species)

Single species in the genus. Many genotypes. Major cause of non-bacterial infectious gastroenteritis; others are astroviruses, adenoviruses.

Question 3

How is norovirus transmitted?

Answer 3

Vomit or stool - direct contact, fomites.

Food (unwell food handler) or water-borne transmission (sewerage contamination).

Highly infectious - low infectious dose. Stable in environment - survives heating, freezing, chlorine. Shedding can be prolonged.

Question 4

What are the clinical features of norovirus?

Answer 4

Vomiting and watery diarrhoea.
Other: abdo pain, nausea, headache, fever, myalgia.

Abrupt onset, vomiting prominent. Usually self-limiting 12-72 hours. High secondary attack usually suggesting of norovirus in an OB situation.

Question 5

Which groups are at high-risk of norovirus disease?

Answer 5

Very young, elderly, medical comorbidities.

Question 6

How is norovirus diagnosed?

Answer 6

Generally clinical.
Detection in stool (PCR) in outbreaks.

Genomic sequencing helpful in outbreaks. Cannot be cultured.

Question 7

What is the incubation period of norovirus?

Answer 7

24 - 48 hours.

Median 32 hours. Range 12-50 hours.

Question 8

What is the infectious period of norovirus?

Answer 8

While symptomatic to 2 days post symptoms.

Question 9

True or False: Norovirus is the leading cause of gastro outbreaks in Australia and worldwide?

Answer 9

True

Significant economic/social impact and health system burden.

Question 10

In which settings are norovirus outbreaks common?

Answer 10

Childcare, residential facilities, hospitals, schools, prisons, cruise ships.

Outbreaks typically seasonal (winter) but not well understood why.

Question 11

What is the case definition of norovirus?

Answer 11

Suspected case: 3+ loose BMs and/or 2+ vomiting in 24 hours + epi association to outbreak.

Confirmed: As above and detection via PCR/EM.

Question 12

What is the outbreak definition for norovirus?

Answer 12

2 or more associated cases of D/V within 24hrs (or a defined timeframe within high-risk settings)

VIC guidelines: care facilities ≥2 cases D/V in 72h, childcare/camp 48h, other settings 24h.

OBs generally person-person but food- or water-borne outbreaks can also occur. Analytical studies may be useful.

Question 13

How is norovirus prevented?

Answer 13

Hand hygiene, food hygiene, IPC, environmental cleaning.

Question 14

Which resources can you use to manage a norovirus outbreak?

Answer 14

CDNA: Guidelines for public health management of gastroenteritis outbreaks due to norovirus or suspected viral agents.

State DoH protocols.

Question 15

How are norovirus cases manged?

Answer 15

• Supportive treatment
• Education (hygiene)
• Cleaning
• Contact precautions + masks
• Isolation, exclusion from work/school

Question 16

For how long should norovirus cases be exluded?

Answer 16

Childcare/school/work - 48hrs post symptom resolution

Isolation/cohorting - 48 hrs post symptom resolution

Question 17

How are norovirus contacts managed?

Answer 17

• Education (hygiene)
• Cleaning
• Isolate and test if Sx develop

Question 18

What environmental management is required for norovirus?

Answer 18

Cleaning with bleach.

If potentially foodborne, consider inspection, sampling, traceback.

If potentially waterborne - inspection/sampling of water source. Refer to council EHU.