Molecular pattern of acquiring upper respiratory infection.

Upper respiratory tract infections (URIs) are a significant public health concern. Human behavior plays a crucial role in how often infected individuals come into contact with susceptible individuals. Among the key factors influencing the seasonality of these infections, variations in temperature and absolute humidity are critical elements driving the increase in respiratory virus infections, particularly during the winter months. Traditionally, it has been believed that cold and flu viruses thrive in winter mainly because falling temperatures lead to people spending more time indoors, which facilitates easier transmission. However, compelling evidence suggests that biological factors also contribute to the increased risk of illness in colder weather. Recent studies indicate that active mucosal defenses against bacteria extend into the mucus itself, aided by the epithelial release of antimicrobial extracellular vesicle (EV) swarms. Unfortunately, these studies have also shown that EVs are significantly weakened by exposure to cold environments.