The disease vectors, in order of relative importance, are human feces, water and food, human contact (including bedding and clothing), insects, and air. During one of the bubonic plagues, an officer moved his troops out of London and into a nearby pine forest; there were no deaths in his camp. Good sanitation can still affect the health and longevity of a population. In a time of pandemic, sick people should be isolated (a separate building); all drinks, eating utensils, and the clothing of the sick should be boiled; all bought food should be cooked; everyone should wash their hands thoroughly after defecating and before food preparation and eating; and living areas should be screened against flies and mosquitoes. Except for the common cold, the most frequent illness today is diarrhea caused by bacteria on raw food or unwashed hands.