Status And Risk Factors Of Norovirus Infection Among Children With Diarrhea In Hangzhou

Background and PurposeNorovirus, a type of human Caliciviridae, was first found in 1972 in USA. Together with Rotavirus, they are the principle enteroviruses contribute for the children's diarrhea. For a long time, due to the lack of simple and sensitive detection means for Norovirus, its harm to human is seriously undervalued. In recent years, with the development of technology, people came to realize the danger of norovirus. It was reported that in developed countries, about 42% to 90% of nonbacterial diarrhea outbreaks were caused by Norovirus. Foodborne Disease Outbreaks Surveillance System of USA indicated that in 1998-2002, Norovirus caused 33% of the food borne disease outbreaks with classified pathogens were caused by Norovirs. In 2006, there was a global pandemic of Norovirus.,In Japan, nearly 3.04 million people infected with some deaths. Norovirus gastroenteritis is becoming a worldwide important public health issue.In China, two strains of norovirus were first found in fecal specimens from acute diarrhea children in Diarrhea Diseases Outpatient in Henan Province in 1990. From then on. sporadic cases of Norovirus infection were also reported in Beijing, Changchun, Wuhan, Guangzhou, etc. The first confirmed outbreak of acute gastroenteritis occurred in Hebei followed by continuous reported cases in Guangdong, Guangxi, and so on. Epidemiological investigation and surveillance has already come into forth in some area of our country. However, there still have no any reports on this in the whole Zhejiang province. To explore the infectious status of Norovirus in Hangzhou as well as to identify the main genotype of virus and related factors to infaction, and to build foundation for the routine surveillance system, we decide to carry out this study. Materials and methodsFecal specimen of under 5 years old patients with clincal diagnosed as Virus Diarrhea in the outpatient of internal medicine of the Zhejiang Children's Hospital were collected from November to December in 2005-2007 and the whole year of 2008. Real-time fluorescent RT-PCR was applied to detect Noroviruse in specimen, while conglutinin agglutination test was used to detect Rotavirus. We also carried out special investigation on the general situation, clinical manifestations, risk factors for infection to these children. Children who visit the outpatient of the surgical department and fever clinic in this hospital at the same period and have no diarrhea within the latest two weeks were chosen as control. We also collected the data of the laboratory confirmed norovirus outbreaks from 2006 to 2008 in Hangzhou to analyze the cause of outbreak and its harm.SPSS13.0 statistical software was used for this study. Single factor analysis were used to analyze the influencing factors of norovirus infection, T test for the numerical variable data of the Gaussian distribution, rank sum test for the numerical variable data of the nonnormal distribution, and Chi-square test for categorical variable data.Statistical significance was designated at P≤0.05. Non conditional Logistic Model regression analysis was performed to determine significant independent contributor to norovirus infection.Results1. A total of 634 fecal specimens of clinical diagnosed viral diarrhea cases were collected and field survey were also implemented to them at the same time. According to the diagnosis criterion,78 cases of Norovirus and 271 cases of Rotovirus were identified. The overall detection rate of norovirus was 12.30%(78/634). The overall detection rate of rotovirus was 42.74%(271/634). We also completed investigation to 161 children as control. There were no combining infection of norovirus and rotovirus. The peak months of virus detection were January, February, November, and December. 2. The main symptoms of Norovirus infected children were gastrointestinal symptoms including fever, diarrhea, and vomiting. Compared with rotovirus infection, children with norovirus are more likely to have syndrome of vomiting.3. Risk factors of norovirus infection include living environment, floating population, family income, hygiene habbits of parents including washing hands after defecation and timely washing rags, breastfeeding.4. The molecular genotyping of the 78 noroviruses showed that GⅡwere in the majority and GⅡ/4 genotype was the prominace genotype in Hangzhou city.5. Seven outbreaks of norovirus gastroenteritis were reported in 2006-2008. All of them happened during winter and spring and person-to-person contact transmission were their major transmission.ConclusionsThis study helps to make it clear that the status of norovirus infection in diarrhea children in Hangzhou City, the main genotype of norovirus, the risk factors of Norovirus infection for children, and the major transmission of norovirus outbreaks. This contributes to a good foundation for the long-time surveillance.