NEW MICROBIOLOGICA, 30, 49-52, 2007 Detection of sporadic cases of Norovirus infection in hospitalized children in Italy Sonia Caracciolo, Chiara Minini, Domenico Colombrita, Ida Foresti, Manuela Avolio, Giorgio Tosti, Simona Fiorentini, Arnaldo Caruso Department of Applied and Experimental Medicine, Section of Microbiology, University of Brescia Medical School, Brescia, Italy This study was performed to investigate the role of Noroviruses (NV) in sporadic cases of acute diarrhoea among hospitalized children in Brescia Hospital. NV were the most frequently involved viruses (23.7%) and were more common in children >5 years (23/63) than in children <5 years (6/59). The majority of the NV-positive specimens belonged to genotype II (GII). The frequency of rotavirus, enteric adenovirus and astrovirus was 12.2%, 1.6% and 2.4%, respectively. Results obtained confirm the relevance of NV as a causative agent of pediatric diarrhoea and highlight the need for continued surveillance of NV to prevent and control virus spreading. KEY WORDS: Gastroenteritis, Norovirus, Molecular epidemiology SUMMARY Received November 29, 2006 Accepted December 5, 2006 Gastroenteritis remains a major public health issue worldwide, especially among children (Giordano et al., 2001). More than 700 million cases of acute gastroenteritis are estimated to occur every year in children under the age of 5 years with a mortality of 3.5-5.0 million per year (Snyder and Merson, 1982). Many different pathogens have been found in the stools of children with gastroenteritis. From them, bacteria, such as Salmonella spp., Shigella spp., and Campylobacter spp. among others, and viruses, such as rotaviruses, adenoviruses (Diamanti et al., 1996) and astroviruses (Donelli et al., 1993) have been clearly established as eti- ologic agents of gastroenteritis in children. More recently, Noroviruses (NV formerly known as “Norwalk-like viruses”) have also been included as a common cause of outbreaks and sporadic cases of gastroenteritis worldwide in individu- als of all ages. NV are a group of single-strand- ed positive-sense RNA viruses belonging to the Caliciviridae family, which includes a large num- ber of genetically related strains. NV can be divid- ed into three distinct genogroups: GI, GII, and GIII (Ando et al., 1995). GI and GII noroviruses infect humans and include 5 and 10 genetic clusters, respectively; GIII noroviruses infect pigs and cows. Thanks to the development of sensitive molecular assays (e.g., reverse transcription-polymerase chain reac- tion), and enzyme-linked immunosorbent assays (ELISA), NV have recently been reported as a major cause of viral gastroenteritis outbreaks in different countries (Lopman et al., 2002; Liu et al., 2006). NV are highly infectious agents whose transmis- sion remains primary faecal-oral, though air- borne and fomite transmission may also con- tribute to the virus spreading during outbreaks. It is often difficult to link secondary or tertiary cases resulting from person-to-person contact to a specific mode of transmission (Fretz et al., 2005). Nevertheless very few studies so far have Corresponding author Arnaldo Caruso University of Brescia Medical School Piazzale Spedali Civili, 1 25123 Brescia, Italy E-mail: caruso@med.unibs.it