COLD SEASONS AND VIRUSES
It is in the cold months of the year (autumn and winter) when the population suffers the highest number of viral respiratory infections. You are talking about the common cold and the flu.
These infections account for half of all acute infections. Cold temperatures modify circulatory conditions in nasal mucosa (layer that covers the inside of the nose), make it easier for viruses to penetrate and, therefore, infections to develop.
But the factor that most influences the spread of these viral infections is the fact that, due to the cold, you tend to meet in closed-in, unventilated spaces for longer periods: bars, shops, cinemas, school classrooms…, which facilitates the transmission of the virus from person to person.