Epidemiological characteristics of infectious diseases among homeless individuals with mental illness and development of a seamless care model in Southern China

Homeless individuals with mental illness represent a highly vulnerable population with limited access to healthcare, poor living conditions, impaired self-care capacity, and increased susceptibility to infectious diseases. However, epidemiological data on infectious diseases in this population remain limited, particularly in China. This retrospective study aimed to investigate the prevalence, distribution, and variables associated with infectious diseases among homeless individuals with mental illness and to propose a seamless care model for integrated management. This retrospective cross-sectional study included 617 homeless individuals with mental illness admitted to a social welfare psychiatric facility in Haikou, China. Demographic characteristics, psychiatric diagnoses, and laboratory-confirmed infectious disease status were abstracted from institutional records and structured admission assessments. Binary logistic regression was used to identify variables associated with infectious disease status. A seamless care model was developed based on the epidemiological findings, a structured literature review, and stakeholder interviews. The study was approved by the Ethics Committee of Hainan Provincial Anning Hospital with a waiver of individual informed consent. Among the 617 participants, 131 were diagnosed with at least one infectious disease, corresponding to a prevalence of 21.23% in the sampled population. Most infected individuals had a single infection, whereas 8.40% had co-infections. Viral hepatitis was the most common infectious disease, accounting for 66.41% of infected cases, followed by syphilis, pulmonary tuberculosis, and HIV/AIDS. In multivariable logistic regression, male sex, unemployment or unknown occupational status, unmarried status, and psychiatric diagnosis were significantly associated with infectious disease status. Based on these findings, a seamless care model was proposed that integrates mobile screening, electronic health records, rapid referral, standardized treatment, health education, psychosocial rehabilitation, and intersectoral collaboration. Infectious diseases were frequently identified among homeless individuals with mental illness in this single-center southern China cohort, with viral hepatitis and syphilis representing the major disease burden. Demographic vulnerability, social instability, and psychiatric diagnosis were associated with infectious disease status, although the cross-sectional design precludes causal inference. The proposed seamless care model provides a structured framework for early detection, continuous treatment, rehabilitation support, and public health coordination in this marginalized population. Future multicenter and prospective studies are warranted to validate the effectiveness and scalability of this model.