Surveillance of infectious diarrhea patients in Shanghai during 2013-2016, based on establishment of diarrhea public health comprehensive surveillance system

Objective To introduce the establishment of Shanghai Diarrhea Comprehensive Surveillance System, and to analyze the epidemiological and etiological characteristics of infectious diarrhea outpatients in Shanghai based on data of Shanghai Diarrhea Comprehensive Surveillance System. Methods Diarrhea patients were surveyed according to a unified designed questionnaire, who visited one of 22 adult sentinel hospitals and 4 children sentinel hospitals of Shanghai Diarrhea Comprehensive Surveillance during September 2013 to August 2016. Stool specimens were collected according to different sampling intervals and detected for 12 bacteria and 5 viruses. Characteristics of diarrhea patients were compared and analyzed. Chi-square test was used for statistical analysis. Results Of 4 497 infectious diarrhea patients, the detection rate of viral infection was 29.77%, of which norovirus infection (16.33%), rotavirus infection (7.90%) and sapovirus infection (1.90%) were dominated. The detection rate of bacterial infection was 15.38%, diarrheagenic E. coli (DEC) infection (5.25%), V. parahaemolyticus infection (4.27%) and Salmonella spp. infection (3.13%). Mixed infection accounted for 11.07%. The detection rate, the infection types and the predominant pathogens in different age groups were statistically different (χ2=18.11, 61.86 and 449.52, respectively, all P<0.01). DEC ranked first in 3-14 years age group, and norovirus ranked first in all other age groups. The pathogen spectrum of infectious diarrhea patients ≥15 years old showed obvious seasonal changes, with mainly bacterial infection in summer (peaked in August, accounting for 81.56%) and mainly viral infection in winter (peaked in January, accounting for 95.27%). Norovirus ranked first through the year, except January, June, July and August. Among patients ≥15 years old, abdominal pain, fever and loose stools were main symptoms in bacterial infections. Vomiting and watery stool were main symptoms in viral infections. Loose stools appeared frequently in patients ≤14 years old. Conclusions Diarrhea Comprehensive Surveillance System based on scientific design and rational distribution is beneficial for understanding the epidemic trends and pathogen characteristics of diarrhea. Viral infections are predominant in infectious diarrhea patients in Shanghai. Norovirus and rotavirus are the most common diarrheal pathogens. The pathogen spectrum of infectious diarrhea patients shows obvious seasonal changes. DEC is common in diarrhea patients ≤14 years old. The clinical symptoms of infectious diarrhea caused by different pathogens are different. Targeted preventive measures should be taken for infectious diarrhea of different ages, different pathogens, and in different seasons. Key words: Diarrhea; Comprehensive surveillance; Epidemiology; Etiology