Given the health risks caused by the presence of pathogenic bacteria in food and the occurrence of diarrhea as one of the most common diseases, a comprehensive epidemiological study in a specific population can provide good results on the causes of occurrence to determine ways to prevent and control the disease. Thus, due to the lack of domestic statistics in Iran related to outbreaks caused by water and food, this study was carried out to identify the most common bacterial factors causing outbreaks caused by foodborne diseases in Semnan province.

This study was carried out on all the outbreaks caused by food items in Semnan province for 1 year, from April to March 2020.

The samples were examined to isolate and identify the bacteria of Salmonella, Shigella, and Escherichia coli O:157: H7. The required information was completed based on the questionnaire and laboratory data, and the study results were analyzed in SPSS-19 software.

The results revealed that the frequency of outbreaks was observed in women more than in children and men (46%). The frequency of outbreaks in 24–44 years was observed more than in other groups (31.57%). The frequency of outbreaks was more in the city (57.31) than in the village (42.69), and among the cities, Semnan had the highest frequency (32%), and Sorkheh had the lowest frequency (5.26%). The frequency of outbreaks caused by consuming food was more than water, and the frequency of outbreaks caused by consuming fast food (55.55%) was more than homemade food (44.45%). More than half of the bacterial frequency belonged to E. coli species (73%). The lowest bacterial frequency belonged to Proteus vulgaris species with (1.7%), followed by Shigella and Salmonella with 2.9% bacterial frequency. The results of clinical symptoms showed headache, (88.2%) fever, (92.2%) abdominal cramps, (58.8%) vomiting, (58.8%) nausea, (66.7%), nonbloody diarrhea, and bloody diarrhea was observed in 3.9% of people.

According to the results of this study, E. coli can be considered one of the essential causes of diarrhea caused by food outbreaks.