In the 2012-2013 winter season, ISGEV reports the emergence of a novel norovirus (NoV) variant, GII.4 Sidney 2012. About 75% of the NoV analysed strains between November 2012 and January 20013 were characterised as GII.4 Sidney 2012.

Noroviruses (NoVs) are a major cause of acute gastroenteritis in both children and adults, being responsible for sporadic cases and outbreaks of gastroenteritis in various epidemiological settings. A single NoV genotype, GII.4, has been associated with the vast majority of NoV-related outbreaks and sporadic cases of gastroenteritis worldwide (Bok et al., 2009).

GII.4 NoV strains periodically generate novel strains via accumulation of punctate mutations or recombination. New GII.4 variants emerge every 2-3 years (Siebenga et al., 2007; Lindesmith et al., 2011). Increased incidence of norovirus-related outbreaks and or illness in various countries in the late 2012 has been related to the emergence of a novel GII.4 variant, Sydney 2012. This variant was first identified in March 2012 in Australia (van Beek et al., 2013) and in the capsid gene has a common ancestor with the former NoV GII.4 variants Apeldoorn 2008 and New Orleans 2009, although phylogenetically distinct, and several amino acid changes are seen in the main epitope on the P2 domain. In addition, the novel variant has a polymerase gene of recombinant origin, GII.Pe.

ISGEV monitors the epidemiology of enteric viruses in children through hospital-based surveillance. Two epidemiological observatories, in Palermo and Parma are currently involved in this specific task. Monitoring and characterization of NoVs is achieved by a multi-target analysis in the diagnostic regions A, B, C, E and D of NoV genome (Kroneman et al., 2011)and interrogation of the Norovirus Typing Tool database  (http://www.rivm.nl/mpf/norovirus/typingtool).

During the late 2012 (November-December) and January 2013 the ISGEV monitored a high prevalence of NoV infection in children hospitalized or visitedfor gastroenteritis (90/311, 28.9%) and 74.3% of the NoV analysed strains were characterised as GII.4 Sidney 2012, confirming the epidemiological relevance acquired in other European and extra-European countries by the new NoV variant Sidney 2012. Continued surveillance for NoV infections through ISGEV and additional data on clinical and epidemiologic features will enable further assessment of the public health implications of the new variant GII.4 Sydney 2012 in Italy. Proper hygiene measures (thoroughly washing and disinfection of hands, environmental disinfection, isolation of ill persons) are pivotal for NoV prenvention and control.

The detailed report has been published on Emerging Infectious Disease  (Giammanco et al., 2013).

Literature 

1.         Green KY. Caliciviridae. In: Knipe DM, Howley PM, Griffin DE, Lamb RA, Martin MA, Roizman B, et al., editors. Fields virology. 5^th ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2007. p. 949-79.

2.         Kroneman A, Vega E, Vennema H, Vinjé J, White PA, Hansman G, et al. Proposal for a unified norovirus nomenclature and genotyping. Arch Virol. 2013; In press.

3.         Bok K, Abente EJ, Realpe-Quintero M, Mitra T, Sosnovtsev SV, Kapikian AZ, et al. Evolutionary dynamics of GII.4 noroviruses over a 34-year period. J Virol. 2009 Nov;83(22):11890-901. PubMed PMID: 19759138.

4.         Siebenga JJ, Vennema H, Renckens B, de Bruin E, van der Veer B, Siezen RJ, et al. Epochal evolution of GGII.4 norovirus capsid proteins from 1995 to 2006. J Virol. 2007 Sep;81(18):9932-41. PubMed PMID: 17609280.

5.         Lindesmith LC, Donaldson EF, Baric RS. Norovirus GII.4 strain antigenic variation. J Virol. 2011 Jan;85(1):231-42. PubMed PMID: 20980508.

6.         van Beek J, Ambert-Balay K, Botteldoorn N, Eden J, Fonager J, Hewitt J, et al. Indications for worldwide increased norovirus activity associated with emergence of a new variant of genotype II.4, late 2012. Euro Surveill. 2013;18(1). PubMed PMID: 23305715.

7.         Medici MC, Tummolo F, Albonetti V, Abelli LA, Chezzi C, Calderaro A. Molecular detection and epidemiology of astrovirus, bocavirus, and sapovirus in Italian children admitted to hospital with acute gastroenteritis, 2008-2009. J Med Virol. 2012 Apr;84(4):643-50. PubMed PMID: 22337304.

8.         Giammanco GM, Rotolo V, Medici MC, Tummolo F, Bonura F, Chezzi C, et al. Recombinant norovirus GII.g/GII.12 gastroenteritis in children. Infect Genet Evol. 2012 Jan;12(1):169-74. PubMed PMID: 22067516.

9.         De Grazia S, Medici MC, Pinto P, Moschidou P, Tummolo F, Calderaro A, et al. Genetic heterogeneity and recombination in human type 2 astroviruses. J Clin Microbiol. 2012 Nov;50(11):3760-4. PubMed PMID: 22933603.

10.       De Grazia S, Martella V, Chironna M, Bonura F, Tummolo F, Calderaro A, et al. Nationwide surveillance study of human astrovirus infections in an Italian paediatric population. Epidemiol Infect. 2013 May 17:1-5. PubMed PMID: 22592003.

11.       Kroneman A, Vennema H, Deforche K, v d Avoort H, Penaranda S, Oberste MS, et al. An automated genotyping tool for enteroviruses and noroviruses. J Clin Virol. 2011 Jun;51(2):121-5. PubMed PMID: 21514213.

12.       Fonager J, Hindbaek L, Fischer T. Rapid emergence and antigenic diversification of the norovirus 2012 Sydney variant in Denmark, October to December, 2012. Euro Surveill. 2013;18(9). PubMed PMID: 23470017.