Description

Norovirus GI/GII. Noroviruses are highly contagious members of the Caliciviridae family of RNA viruses and can be divided into five genogroups (GI – GV). GI, GII, and GIV have been found most commonly in humans (though GIV is very rare) where they cause moderate to severe gastroenteritis consisting primarily of nausea, vomiting, and diarrhea accompanied by fever. Transmission occurs via the fecal-oral route or through aerosolized vomitus and the infectious dose may be as low as 18 particles.48 Symptoms of infection generally last 24-48 hours49 and the illness is self-limiting; though immunocompromised persons may suffer chronic diarrhea and some children have been reported to develop necrotizing colitis. Outbreaks are common in closed communities such as cruise ships, hospitals, nursing homes, schools, and military installations. Norovirus infections are the leading cause of foodborne gastroenteritis in the US, causing nearly 5.4 million illnesses (and over 14,000 hospitalizations) annually12 and are also a significant source of illness in the EU.13 Peak infection rates occur during winter months.50 Immunity following Norovirus illness is short lived as re-infection is possible within 6 months, even in the presence of high serum antibody titers.51