Viral Agents Of Acute Gastroenteritis Among Infants And Children In Lanzhou City, China During 2005-2006: Prevalence And Molecular Diversity

Backgroud: Gastroenteritis disease is a major cause of childhood morbidity and mortality; especially in developing countries.Globally almost 1.5 to 2 million infants and young children are believed to die of gastroenteritis-related disease or complications every year. Enteric virus have been recognized as the most important etiologic agents of disease, and four categories of viruses are now considered as clinically important including rotavirus,calicivirus,adenovirus and astrovirus. Rotavirus is recognized to be the single most important etiological agent associated with severe dehydrating gastroenteritis. Each year, rotavirus causes approximately 440,000-6000, 000 deaths in children <5 years of age. Rotavirus Vaccine is the single effective method to prevent and control rotavirus diarrhea morbidity and mortality. The fluctuations of predominant strains depending on the area and the year studied have confirmed the importance of long-term and systematical surveillance in a variety of geographical settings and provided important considerations for the development and implementation of an effective vaccine.Objective: To study molecular epidemiology of four major etiological viruses among children with diarrhea in Lanzhou, Gansu province, and to provide the theory evidence for prevention and treatment to virus diarrhea.Methods: A total of 257 stool specimens were collected from children less than 5 years old with acute gastroenteritis admitted in the First Hospital of lanzhou University from July 2005 to June 2006. Dako IDEIA^TM kits were used for detection of rotavirus, further strain characterization of rotavirus was carried out with reverse transcription-polymerase chain reactions (RT-PCR).The detection of calicivirus, adenovirus and astrovirus were done by multiple (RT-) PCR. The PCR products (DNA) positive for samples of norovirus, adenovirus and astrovirus were analyzed by nucleotide sequencing, respectively.Results: At least one viral agent was found in 72% (186/257) of the specimens. Rotavirus was detected in 60.7 (156/257) of cases, adenovirus 5.4%(14/257), calicivirus 5.1%(13/257),astrovirus5.1%(13/257) respectively. Dual infections were found in 3.5 %(9/257) of all samples. Among 156 rotavirus positive samples, serotype G1 (61.5%)was the most predominant strain followed by G3(25.0%),G2 (3.2%),G9 (2.7%), and mixed-G infection (3.2%), 4.5% of strains remained to be non-typeable.P genotyping showed P[8] (75.6%) was most common followed by P[4] (3.8%) ,mixed-P infection(0.64%), nontypeable 19.9%.Strain P[8]G1(65.0%) was the most common combination followed by P[8]G3(26.0%),P[4]G2(2.4%) and P4G1(1.6%)。The overall prevalence of calicivirus infection was 5.1 % with 93% of the strains belong to the norovirus G II genera. Sequence analysis showed that adenovirus detected in this study belonged to three distinct subgenera(A,C,F)with six serotypes(Ad12,Ad18, Ad2,Ad6, Ad40,Ad41).A total of 13 astrovirus strains were all belongs to astrovirus type 1.A peak admission of rotavirus diarrhea was observed from September through December .More than 94.87% of rotavirus diarrhea patients under hospitalization occurred among children younger than 2 years. The incidence rates of rotavirus were highest in infants aged 6-23 months.Conclusion: Enteric viruses were confirmed as the most common cause of acute gastroenteritis among infants and children in lanzhou.Rotavirus was the most important pathogen for viral gastroenteritis followed by adenovirus, norovirus and astrovirus.The predominant rotavirus strain circulated was P[8]G1,which was different from the finding in the previous years.