This article presents a mathematical model designed to simulate the impact of targeted interventions aimed at preventing HIV transmission among female sex workers (FSWs) and their clients, while also analyzing their effects on the health of the general population. The compartmental model distinguishes between high-risk populations (FSWs and their clients) and low-risk populations (sexually active men and women in the general population), and links prevention efforts in high-risk groups to the evolution of the epidemic in the low-risk population. The fundamental properties of the model, such as the positivity of solutions and the boundedness of the system, have been verified, and the basic reproduction number R₀ has been calculated. Finally, the stability of the model was studied using Varga’s theorem and the Lyapunov method. Simulation results show that targeted prevention among FSWs and their clients reduces HIV incidence in the general population. This framework provides a valuable tool for guiding policymakers in the design of effective strategies to combat the epidemic, especially relevant in the context of suspension of USAID funding.

Legionnaires' disease became widely known following an outbreak of pneumonia in the United States in 1976. It is often caused by infection from artificial water sources such as cooling towers, water supply and heating systems, and recirculating hot tubs. To effectively implement infection prevention measures for Legionnaires' disease, collaboration among healthcare workers, water supply and heating system managers, building hygiene personnel, and other relevant parties is essential. It is important to note that outbreaks of Legionnaires' disease continue to occur frequently both domestically and internationally. While the number of reported cases of Legionnaires' disease in Japan has increased, the mortality rate has decreased but has stabilized at a lower level. Caution is also required as reports have been made in association with disasters and travel, in addition to artificial environmental water.

Respiratory syncytial virus (RSV) is commonly known as a pathogen of the bronchiolitis in children, however, recently also as a pathogen of the severe virus pneumonia in adults, especially elderly persons, and vaccines for elderly persons have been developed. There are two vaccines, such as the vaccines targeted for subgroup A with the adjuvant, and that targeted for both subgroup A and B but not included the adjuvant in Japan. Both vaccines are considered effective to prevent not only the incident of RSV infection/pneumonia, but also the exacerbations of the elderly persons with underlying diseases including chronic cardiopulmonary diseases.

COVID-19 vaccines have demonstrated efficacy in reducing the prevalence of serious illnesses. The relative risk of hospitalization and mortality for patients who get breakthrough infections after immunization versus those who develop reinfections after a prior spontaneous infection is examined in this correspondence. Based on a study on U.S. Veterans who were not vaccinated and experienced reinfections had a much higher risk of experiencing severe illness outcomes compared to those who had received immunizations and experienced breakthrough infections, even if the rates of reinfection and breakthrough infection were similar. Our findings highlight the value of immunization in reducing severe COVID-19 outcomes, even in the presence of reinfections.