**1. Introduction (Virology of Norovirus)**

Norovirus has been identified to constitute a key biological cause of gastroenteritis worldwide [1]. It is also the most common cause of gastroenteritis world over [1]. Norovirus causes an estimated 1.1 million hospitalizations and up to 218,000 deaths among children less than 5 years annually [1]. Clinical manifestations of norovirus infection are characterized by non-bloody diarrhea, vomiting and stomach pain [2]. Incubation period is usually within 12 to 48 hrs after infection with the virus [3]. Complications are uncommon, but may include dehydration, especially in the young, the old, and those with other health problems [3]. Norovirus is typically spread by faeco-oral route, through contaminated food or water or from person to person [4]. Potential risk factors are poor environmental hygiene and overcrowded living quarters [5]. Vomiting, in particular, transmits infection effectively and appears to allow airborne transmission [5].
