Abstract
<title>Abstract</title> <p>Background 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 study aimed to investigate the prevalence, distribution, and associated factors of infectious diseases among homeless individuals with mental illness and to develop a seamless care model for integrated management. Methods This 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 collected through institutional records and structured assessments. Binary logistic regression was used to identify factors associated with infectious disease status. In addition, a seamless care model was developed based on epidemiological findings, literature review, and stakeholder interviews. Results Among the 617 participants, 131 were diagnosed with at least one infectious disease, yielding an overall prevalence of 21.23%. 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. Multivariable logistic regression showed that 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, integrating mobile screening, electronic health records, rapid referral, standardized treatment, health education, psychosocial rehabilitation, and intersectoral collaboration. Conclusions Infectious diseases are common among homeless individuals with mental illness in southern China, with viral hepatitis and syphilis representing the major disease burden. Demographic vulnerability, social instability, and psychiatric conditions may jointly contribute to infection risk. 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.</p>