[Climate, environment, and respiratory tract infections].

Climatic factors (temperature, wind, humidity) and their changes play a major role in the epidemiology of infectious diseases, mainly those vector borne or water-borne. In terms of respiratory tract infections, the role of cold remains controversial, although evident in popular belief: the winter peak is multifactorial, but exposure to cold causes a vasoconstriction of the nasal and upper respiratory tract mucosa, which decreases the local defense, and allows latent viral infections to become patent. The prevention of hand transmission remains essential. The role of wind in the transmission of pathogens able to survive outdoors was studied in the south of France for Coxiella burnetii. A correlation was found between the wind blowing across the Crau plain and cases of acute Q fever downwind, 2 months later.