Norovirus – Credit HPA
Over the past few months we’ve seen numerous reports of norovirus outbreaks in the UK, the United States, and elsewhere around the world. While hardly an uncommon virus, the level of activity has seemed unusually heavy this year.
A few recent blogs on norovirus include:
Like influenza viruses, when we talk about noroviruses, we aren’t talking about a single entity, as there are many different serotypes and strains.
There are currently five different genogroups (GI, GII, GIII, GIV, and GV) of noroviruses, with most human infections stemming from GI and GII. Within each genogroup, there are multiple subtypes.
GII noroviruses have at least 19 subtypes. The most common cause of human illness is from Genogroup II, genotype 4 (abbreviated as GII.4).
And as with influenza viruses, these single-stranded RNA viruses are rapidly evolving pathogens, so we typically see a new norovirus strain emerge every two or three years.
In 2009, we saw the emergence of the New Orleans strain of GII.4.
Earlier this year, a new variant of GII.4 was isolated in Sydney, Australia and since then has been reported in Japan, the Netherlands, and the UK. In the United States, this variant is commonly called Sydney 2012.
All of which serves as prelude to a report in today’s Eurosurveillance Journal on the emergence, and spread, of this new variant GII.4 norovirus.
While more surveillance data is needed to accurately determine this new strain’s impact, the author’s warn that health care facilities should prepare for a severe norovirus season.
Excerpts follow, but hit the link to read the report in its entirety.
Eurosurveillance, Volume 18, Issue 1, 03 January 2013
J van Beek , K Ambert-Balay, N Botteldoorn, J S Eden, J Fonager, J Hewitt, N Iritani, A Kroneman, H Vennema, J Vinjé, P A White, M Koopmans, on behalf of NoroNet
Date of submission: 18 December 2012
Globally, surveillance systems showed an increase in norovirus activity in late 2012. Molecular data shared through the NoroNet network suggest that this increase is related to the emergence of a new norovirus genotype II.4 variant, termed Sydney 2012. Healthcare institutions are advised to be prepared for a severe norovirus season.
In the United Kingdom (UK), the Netherlands, and Japan, norovirus (NoV) epidemiological and laboratory surveillance systems show increased levels of NoV activity compared to previous seasons, in late 2012 [1-3]. Similarly, increases have been noted in Australia, France and New Zealand (unpublished data). At this stage, and with the limited surveillance of NoV in most countries, it is difficult to conclude if these increases denote early seasonal activity or truly increased incidence, although for the UK the latter has been suggested.
On 29 November, and on 4 and 6 December, ProMed (http://www.promedmail.org/) messages reported a dramatic rise in NoV hospital outbreaks in England, a 64% higher number of confirmed NoV laboratory reports (hospital- and community-acquired) in England and Wales, and NoV-related deaths in elderly in Japan.
The first molecular data uploaded to the international molecular surveillance database NoroNet from Australia, France, New Zealand and Japan indicate that this increase is associated with emergence of a new variant of genotype II.4 (GII.4). The first report of this variant was from Australia in March 2012 (personal communication P.A. White, September 2012), and the strain sequence was submitted to GenBank (accession number: JX459908.1).
In the United States (US), the variant (named Sydney 2012) was detected in September 2012 in five of 22 (23%) laboratory-confirmed outbreaks, and in November in 37 of 71 (52%) laboratory-confirmed outbreaks (recorded in the US norovirus surveillance network CaliciNet) . In two European countries that have not reported any indications of increased activity, the new variant has been found in outbreaks, two in Belgium (September and December 2012) and one in Denmark (November 2012). Other countries participating in NoroNet have not yet reported the new variant.
Various countries around the globe have reported a higher incidence of NoV outbreaks or illness late 2012, and the first molecular data available via NoroNet suggests that this increase is related to emergence of a new variant of NoV GII.4.
More data is needed to confirm the association between a higher NoV incidence and the new NoV GII.4 2012 variant. For this, we invite new members to join the NoroNet network (http://www.noronet.nl).
Noronet is a worldwide network for NoV molecular and epidemiological surveillance, through which countries in Europe, Asia, and Australasia have shared NoV outbreak data, sequences, and other information. The NoroNet database, including analysis tools, is accessible for all NoroNet members.
With the early signs of a severe NoV season, healthcare institutions are advised to be prepared for NoV introductions. Outbreak management measures, like stringent hygiene measures and quarantine of infected cases, can help to reduce the size of outbreaks [14,15].