Background Leptospirosis is an emerging zoonotic disease with high incidence in tropical regions such as the Peruvian Amazon. Although it affects individuals of all ages, knowledge about its clinical and epidemiological behavior in children under five years old remains limited. This population may present atypical clinical forms, nonspecific symptoms, and a milder course, increasing the risk of underdiagnosis and delayed treatment. Methodology A descriptive and retrospective study was conducted by reviewing medical records and epidemiological forms of all MAT-confirmed patients from 2022 to 2024 in primary health centers in Belén, the district with the highest historical prevalence in Loreto. A total of 400 cases out of 1666 reported were included. Among children under five (n=28), clinical presentation was predominantly nonspecific, with malaise (78.6%) and fever (71.4%) being most frequent. Nearly half (46%) sought care within the first three days of symptoms, and 50% lived in flood-prone areas. Nutritional status showed a significant association, with a predominance of underweight (p<0.001), remaining significant in multivariate analysis (OR=0.051; 95%CI: 0.011–0.233; p<0.001). Additionally, each additional day of illness was associated with an increased likelihood of belonging to this age group (OR=1.366; 95%CI: 1.135–1.644; p=0.001). Regarding serovars, Panama showed significant association with children under five (p=0.024), whereas Hurstbridge was absent. Conclusion Children under five with leptospirosis exhibit a distinctive clinical and epidemiological profile, characterized by nonspecific symptoms, higher frequency of underweight, and earlier healthcare-seeking behavior. Associations with malaise, poor nutritional status, and specific serovars like Panama suggest a less typical presentation, potentially hindering diagnosis at the primary care level. These findings highlight the need for tailored surveillance, diagnostic, and management strategies for this age group, particularly in endemic regions such as the Peruvian Amazon.

The authors have declared no competing interest.

The author(s) received no specific funding for this work.

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The study was approved by the Ethics Committee of the Regional Hospital of Loreto “Felipe Santiago Arriola Iglesias” (Comité Institucional de Ética en Investigación – CIEI-HRL). Approval number: 091-CIE-HRL-2024. The research was conducted in compliance with national and institutional ethical guidelines. All patient data were anonymized prior to analysis, and informed consent was not required as the study involved retrospective review of de-identified clinical records.

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