norovirus
Table of Contents
norovirus
see also:
Introduction
- one of the most common causes of acute gastroenteritis (18% of global cases), and presents as sudden onset vomiting and diarrhoea
- it is highly contagious and is more common in winter
- outbreaks occur in residential care facilities, hospitals, schools and child care centres
Virology
- non-enveloped RNA Caliciviridae virus
- noroviruses can genetically be classified into five different genogroups (GI, GII, GIII, GIV, and GV), which can be further divided into different genetic clusters or genotypes.
- Groups 1, 2, 3 and 4 last shared a common ancestor in 867 AD
- it can survive for months, maybe even years in contaminated still water
- it can survive for weeks on most surfaces
- it is destroyed when food is heated above 75deg C
Human genetic factors
- a non-functional fucosyltransferase FUT2 provides high protection from the most common norovirus strain, GII.4.
- homozygous carriers of any nonsense mutation in the FUT2 gene are called non-secretors, as no ABH-antigen is produced
- 20% of Caucasians are non-secretors due to G428A and C571T nonsense mutations in FUT2 and therefore have strong protection from GII.4
Incubation period
- 24-48hrs
Spread
- only need 5-20 virus particles to cause an infection!
- when a patron at a restaurant vomited on the floor which was quickly cleaned up, the attack rate was 90% at her table, 70% at the adjacent table and even 25% at the most distant table!
- direct contact (or indirect contact via fomites) of vomitus or stool (eg. shaking hands, sharing drinks)
- airborne particles when people vomit (eg. after toilet flush or vomit onto floor)
- eating oysters and other shellfish which have lived in water contaminated with norovirus
- eating food that has been handled by infected persons eg. salads
Clinical features
- sudden onset vomiting and diarrhoea
- may also have nausea, fever, abdominal cramps, headache, myalgias
- recovery usually occurs within 1-3 days but globally causes 200,000 deaths pa mainly in the developing world, and mainly in the very young, the elderly or the immunocompromised
- patient remains infectious from onset to at least 48hrs after resolution although some can remain up to 2 weeks after recovery
Mx
- isolate - contact precautions
- hand hygiene, etc
- supportive care
- oral rehydration solutions
norovirus.txt · Last modified: 2019/06/15 10:25 by 127.0.0.1