Risk Factors for Sporadic Non-Typhoidal <i>Salmonella</i> Infection Among Children Under Five Years of Age in an Urban Area of Kunming City: A Matched Case–Control Study

Although urbanization in China has improved access to clean water and sanitation, thereby reducing the transmission of fecal-oral pathogens, non-typhoidal Salmonella (NTS) infection remains relatively prevalent among children. The study aims to explore risk factors associated with NTS infection in young children in urban city areas. An age- and sex-matched, case–control study was conducted from May 2022 to April 2023. One hundred one cases and two hundred two controls who were residing in the urban area of Kunming City were interviewed using a standardized questionnaire on exposures 3 days before illness. The association of each exposure with infection status was determined using conditional logistic regression. NTS infections peaked during the rainy season (May–October). Salmonella Typhimurium was the predominant serotype (64.5%), followed by Salmonella Enteritidis (11.8%). Multivariable analysis revealed that refrigerated storage of raw eggs (adjusted odds ratio [aOR] = 4.73; 95% confidence interval [CI]: 2.02–11.05), lack of a separate cutting board for raw and cooked foods (aOR = 10.38; 95% CI: 3.81–28.32), and higher household density (≥2 children: aOR = 2.69; 95% CI: 1.18–6.16; ≥3 children: aOR = 10.16; 95% CI: 2.90–35.60) were independently associated with increased risk of NTS infection. In addition to household hygiene practices, household crowding was identified as a key amplifier of NTS transmission risk. These findings underscore the need for integrated public health strategies that combine targeted hygiene education with structural interventions to reduce overcrowding in urban households.