<s>[INST] Why do colds and the flu increase in the winter? [/INST] Cold weather itself does not cause colds, but people are more likely to stay indoors and spread cold germs to one another when it's cold outside. There is emerging evidence that influenza spreads most efficiently at low temperatures and in low humidity, which may explain why cases of the flu increase so much in the winter. Source: Harvard Health Publishing . Link: https://www.health.harvard.edu/diseases-and-conditions/frequently-asked-questions-about-colds-and-the-flu. Field: General Medicine. Disease: Cold </s>