The principle of Undetectable = Untransmittable (U=U) posits that people living with the human immunodeficiency virus (HIV) who are able to achieve and maintain a viral load of <200 copies/mL by regularly taking antiretroviral drugs (ARVs) are considered virally suppressed and cannot transmit the HIV virus to other individuals through sex. This groundbreaking message has emerged as a key HIV prevention strategy for eliminating transmission risks and enhancing the quality of life of people living with HIV. This narrative review explores the clinical foundation of U=U, the level of awareness and acceptance of the message globally, and the psychosocial impact on people living with HIV. It has been discovered that this message minimizes stigma, improves mental health, promote treatment adherence and good disclosure behaviors among people living with HIV. Evidence has shown that despite the U=U revolution for HIV prevention, there are significant differences in awareness and acceptance of the message among different population groups. The challenges noted were poor communication by healthcare providers, limitations in the health system, and stigma issues. Nevertheless, the inclusion of U=U in mainstream HIV services has proven to increase awareness and enhance its adoption. The urgent need in the present review is to advocate for strategies to increase the equitable distribution of U=U to harness its full potential in public health.

Mathematical modeling plays a central role in infectious disease epidemiology, shaping outbreak response strategies and informing public health policy. The COVID-19 pandemic demonstrated the value of these models but also exposed persistent limitations related to data fragility, lack of transparency, limited stakeholder engagement, and insufficient consideration of social and political contexts. Rather than critiquing modeling as a discipline, this perspective argues for a reorientation of infectious disease modeling toward a more responsive, equity-centered, and participatory paradigm. We propose a conceptual framework built on three interrelated principles: adaptability through real-time data integration, transparency via open-source and reproducible practices, and relevance through interdisciplinary and co-produced model design. Drawing on illustrative examples from COVID-19 and dengue control efforts, we highlight how integrating behavioral dynamics, local knowledge, and policy feedback can improve model usefulness and public trust. Reconceptualizing models as dynamic systems of inquiry rather than static forecasting tools can enhance decision-making and promote more equitable and effective responses to future public health emergencies.

<b>Background: </b>Tobacco control policies nationwide have contributed to a substantial decline in cigarette and tobacco use, with particularly sharp reductions observed in states such as California that have implemented restrictive bans, strong prevention measures, and high excise taxes. While these policies have led to overall decreases in tobacco use, progress has not necessarily been distributed equally across racial groups. Understanding long-term trends by race is critical for addressing equity gaps in tobacco prevention and control. Evidence suggests that some racialized groups may experience slower or delayed declines, raising concerns about equity in public health gains. <b>Methods: </b>We analyzed data from the California Health Interview Survey (CHIS) spanning 2003–2023. Trends in current smoking were examined separately for non-Latino Black and non-Latino White adults. We also assessed current use of flavored tobacco products, given California’s statewide ban enacted in 2021. Changes were evaluated in both absolute terms (percentage point declines) and relative terms (percent reduction from baseline). <b>Results: </b>Smoking prevalence declined from 17.2% in 2003 to 5.2% in 2023 among White adults and from 19.9% to 9.0% among Black adults. This represents a 12.0 percentage point (69.8%) decline for Whites compared with a 10.9 percentage point (54.8%) decline for Blacks. For flavored tobacco use, prevalence decreased from 8.0% to 4.7% among White adults but only from 11.9% to 10.8% among Black adults. This corresponds to a 3.3 percentage point (41.3%) decline for Whites compared with a 1.1 percentage point (9.2%) decline for Blacks. <b>Conclusions: </b>Although both Black and White adults in California experienced reductions in smoking over the past two decades, White adults showed larger declines in both absolute and relative terms. Disparities were even more pronounced for flavored tobacco use, where declines were minimal among Black adults despite the statewide ban. These findings suggest that Black populations in California may have been left behind by tobacco control progress, especially regarding flavored products. Given the history of targeted marketing by the tobacco industry, the role of flavors in increasing dependence, and reduced access to cessation resources in Black communities, targeted policies and culturally tailored interventions are needed to ensure equitable reductions in tobacco use. Greater attention to flavored tobacco in Black communities may help narrow these disparities and advance California’s tobacco endgame goals.

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.

<b>Background: </b>Tobacco control policies are implemented globally to reduce tobacco-related morbidity and mortality. Emerging evidence suggests that individual tobacco use may influence the level of support for these policies. However, the extent to which personal use affects policy endorsement remains underexplored, particularly among young adults in academic settings. <b>Aims: </b>This study aimed to examine whether college students who use tobacco exhibit lower support for tobacco control policies compared to their non-user counterparts. <b>Methods: </b>We conducted a multi-center, cross-sectional study involving 2403 college students from various provinces in Iran. Tobacco use was ascertained based on self-reported consumption of cigarettes, electronic cigarettes, and hookah. Attitudes toward tobacco control policies were evaluated using a structured survey instrument, and comparative analyses were performed to assess differences in policy support between tobacco users and non-users. <b>Results: </b>The analysis revealed that tobacco users demonstrated significantly lower support for tobacco control policies compared to non-users. This association was consistently observed across users of cigarettes, electronic cigarettes, and hookah, suggesting a systematic pattern irrespective of the type of tobacco product used. <b>Conclusion: </b>These findings indicated a clear association between tobacco use and reduced endorsement of tobacco control policies among Iranian college students. These results have potential implications for public health policy, emphasizing the importance of addressing individual tobacco use behaviors in the development and implementation of tobacco control strategies. Further research is needed to elucidate the underlying mechanisms of this relationship.

<b>Background: </b>Climate change has raised significant concerns about its impact on health, particularly for vulnerable populations such as children and adolescents. While extensive research has examined physical health effects, limited attention has been given to the influence of extreme heat on developmental and behavioral outcomes. <b>Objectives:</b> This study investigates the association between extreme heat exposure and early puberty initiation (ages 9-10), using data from the Adolescent Brain Cognitive Development (ABCD) study. It further explores how early puberty correlates with behavioral problems and tobacco use initiation. <b>Methods:</b> Data from 11,878 participants in the ABCD study were analyzed to examine the relationship between extreme heat exposure (independent variable) and puberty initiation (outcome). Behavioral problems and tobacco use initiation were evaluated as downstream outcomes of early puberty. Covariates included age, sex, and race/ethnicity, and behavioral problems were assessed using the Child Behavior Checklist (CBCL). Structural equation modeling (SEM) was employed for analysis. <b>Results:</b> Extreme heat exposure was significantly associated with earlier puberty initiation at ages 9-10. Early puberty, in turn, correlated with higher levels of behavioral problems and an increased likelihood of tobacco use initiation. <b>Conclusions:</b> These findings underscore the importance of addressing environmental factors such as extreme heat to reduce risks associated with early maturation, including behavioral and substance use challenges. Targeted interventions and policies are needed to mitigate the impact of extreme heat on child development, and longitudinal studies are essential to confirm these results and inform effective prevention strategies.