Epidemiologic Study For Viral Infantile Diarrhea In Lanzhou Area In 2013-2014

Objective:To analyze the features of epidemiology and clinical characteristics of Group A Rotavirus (GARV), Human Calicivirus (HuCV), Human Adenovirus (HAdV) and Human Astrovirus (HAstV) in Lanzhou area of China from 2013 to 2014, and to provide data support and theoretical basis for the prevention and control of viral diarrhea.Methods:A total of 232 stool samples were collected from hospitalized children less than five years with acute infection diarrhea, in Department of Pediatrics, the First Hospital of Lanzhou University, between July 2013 and June 2014. At same time, personal information and clinical data of those children were collected. Group A rotavirus was identified by enzyme-linked immunosorbent assay (ELISA), while G and P serotypes were identified by nested reverse transcription PCR method. Norovirus was confirmed by reverse transcription PCR method and Adenovirus by PCR method. Sapovirus and Astrovirus were detected by real-time quantitative reverse transcription PCR method.Results:Among the 232 samples,146 samples were detected with virus infection, with a rate of 62.93%, indicating that the virus infection was the primary cause for diarrhea among the infants in Lanzhou area this year. The infection rate of Rotavirus was 40.09%(93/232), which was the most prevalent one among the four viruses, then followed by Calicivirus (41/232,17.67%). The detection rate of Adenovirus and Astrovirus were 7.33% and 6.03% respectively. There were 18 co-infections(7.76%) to be found while most of which were Rotavirus mixing with other viruses.Among the 93 Rotavirus samples, four G serotypes as G1, G2, G3, G9 and two P serotypes as P[4] and P[8] were detected. The detection rates of VP7 serotypes ranked from high to low were as follows:G9(50.54%), G3 (34.41%), G2 (6.45%), G1 (5.37%), G combination (3.23%). The detection rate of G9 showed sharp decrease as compared to the previous year, but remained the principal epidemic strain in Lanzhou area. The detection rates of VP4 serotypes ranked from high to low:P[8] (83.87%), P[4] (10.75%), P non-typeable (3.23%), P combination (2.15%), and P[8] remained the predominant epidemic strain this year. G9P[8] (43.01%) and G3P[8] (33.33%) combinations were the predominant G/P combinations this year. HRVA showed significant peak seasons this year, with its high-risk months occurring in autumn, and mostly found in children aged from 0 to 18 months, peaking at 7-12 months. According to its clinical manifestation, the infants with Rotavirus infection were more likely to get fever, vomiting, depression and other associated symptoms as compared to the infants with common diarrhea.After Rotavirus, Calicivirus became the second major pathogen of acute infantile diarrhea. Among 41 cases of HuCV positive samples,33 cases were detected with Norovirus (14.22%) and 8 cases with Sapovirus (3.45%). HuCV was mostly found in children aged from 7 to 18 months, peaking at 10-14 months, with its high-risk months occurring in autumn and winter this year and sporadically throughout the year. GⅡ.3, GI1.4, GⅡ.6 types were detected in NoV, with GⅡ.4 as the predominant strain, which showed the high homology with GⅡ.4/Sydney2012 variant strain. GⅠ.1, GI.2, GIV types were detected in SaV, primarily GⅠ.1.17 cases of Adenovirus and 14 cases of Astrovirus were detected this year, with a detection rate similar to previous years, a sporadical distribution throughout the year and peaking at 7-12 months. Adenovirus was detected among the samples of subgroup A (type 12 and 31), subgroup B (type 3), subgroup C (type 1 and 5), subgroup F (type 40 and 41 type). Type 41 of subgroup F remained the predominant type. Astrovirus was detected, mainly HAstV-1 (64.29%); HAstV-4 and HAstV-5 were also detected.Conclusion:Rotavirus was the main pathogen for diarrhea in infants in Lanzhou area. The detection rate of G9 type dropped sharply as compared to the previous year but was still the principal epidemic strain in Lanzhou area. The main epidemic strain GⅡ.4 of Norovirus this year showed homology with the variant strain GII.4/Sydney2012 reported in Sydney in 2012. A long-term monitoring is recommended.