Epidemiological Analysis of Viral Diarrhea in Yantai, Shandong, China (2017-2020): Insights into Seasonal Patterns and Viral Agents

This study aimed to investigate the epidemiological characteristics of viral diarrhea in Yantai City, Shandong Province, from 2017 to 2020. A total of 2,773 suspected cases of infectious diarrhea were collected from healthcare institutions across 13 districts and counties in Yantai. Specimens were tested for astrovirus, enteric adenovirus, norovirus genogroups I and II (GI and GII), rotavirus, and sapovirus using nucleic acid detection kits. Positive cases were analyzed to characterize the pathogen spectrum and epidemiological features. Statistical analyses were conducted using chi-square and Mann–Whitney U tests. The detection rates of viral diarrhea were higher during spring and winter. The positivity rates for astrovirus, adenovirus, norovirus GI, norovirus GII, rotavirus, and sapovirus were 1.23%, 3.64%, 1.44%, 8.11%, 17.42%, and 0.61%, respectively. Among these, rotavirus and norovirus GII showed consistently high detection rates across the study period. Children under six years of age had the highest pathogen detection rates, with rotavirus being the predominant agent. The viral spectrum remained relatively consistent across age groups, and no significant changes in age distribution were observed over time. In conclusion, viral diarrhea in Yantai exhibited a clear seasonal pattern, with peaks in spring and winter. The overall detection rate showed an upward trend followed by a decline, with notable changes occurring between 2018 and 2019. Rotavirus was the most prevalent pathogen identified. Children under six years old represented the most affected population. These findings highlight the importance of strengthened surveillance for infectious diarrhea, particularly viral diarrhea among young children.