The article "Seasonality of Respiratory Viral Infections" by Miyu Moriyama, Walter J. Hugentobler, and Akiko Iwasaki reviews the factors contributing to the seasonal nature of respiratory viral infections. The authors highlight the significant impact of environmental parameters, particularly temperature and humidity, on the stability and transmission of respiratory viruses. They also discuss how these environmental factors modulate host immune responses, including intrinsic barriers, inducible innate immunity, and virus-specific adaptive immunity. The review emphasizes the importance of indoor climate, which can be significantly different from outdoor conditions due to heating and air conditioning, and how this affects the transmission of respiratory viruses. The authors provide evidence that low humidity and cold temperatures can impair mucociliary clearance, increase viral stability, and enhance viral transmission. Additionally, they explore the role of vitamin D deficiency and short daylight periods in impairing innate immune responses. The article concludes by discussing the potential of nonpharmaceutical interventions, such as increasing indoor humidity, to reduce respiratory virus transmission and the need for further research to understand the complex interplay between environmental factors and host responses.The article "Seasonality of Respiratory Viral Infections" by Miyu Moriyama, Walter J. Hugentobler, and Akiko Iwasaki reviews the factors contributing to the seasonal nature of respiratory viral infections. The authors highlight the significant impact of environmental parameters, particularly temperature and humidity, on the stability and transmission of respiratory viruses. They also discuss how these environmental factors modulate host immune responses, including intrinsic barriers, inducible innate immunity, and virus-specific adaptive immunity. The review emphasizes the importance of indoor climate, which can be significantly different from outdoor conditions due to heating and air conditioning, and how this affects the transmission of respiratory viruses. The authors provide evidence that low humidity and cold temperatures can impair mucociliary clearance, increase viral stability, and enhance viral transmission. Additionally, they explore the role of vitamin D deficiency and short daylight periods in impairing innate immune responses. The article concludes by discussing the potential of nonpharmaceutical interventions, such as increasing indoor humidity, to reduce respiratory virus transmission and the need for further research to understand the complex interplay between environmental factors and host responses.