Contributions of the elderly to the transmission of HIV/AIDS in China.

In recent years, the number of HIV/AIDS cases shows an upward trend in China, particularly among the elderly, exerting severe effects on public health and social economy. This paper proposes an HIV/AIDS model incorporating sexual transmission and age structure to study the influence of the elderly on HIV/AIDS spread. Theoretically, the explicit expression for the basic reproduction number is obtained, the globally asymptotically stability of disease-free equilibrium and existence and uniqueness of boundary equilibrium are proved. Numerically, we verify the theoretical results. Based on HIV/AIDS data in Sichuan Province, China, four key parameters of the model are estimated. According to the estimated parameters, we find that homosexual transmission plays an important role in newly HIV/AIDS cases among the elderly in recent years. Sensitivity analysis also shows that homosexual transmission in the elderly has the greatest effect on the basic reproduction number. This study not only contributes to a comprehensive understanding of the dynamical spread process of HIV/AIDS but also provides valuable experience for other sexually transmitted diseases.