冬には人々が風邪やインフルエンザを頻繁に得るというのは一般的な知識ですが、何がこれを引き起こしますか？温度と免疫系の関係に起因しますか？それとも、冬に何らかの形で異なる人間の行動によって引き起こされますか？
It is common knowledge that people get colds and the flu more often in winter, but what causes this? Does it stem from a relation between temperature and the immune system? Or is it caused by human behaviour which is somehow different in winter?