What were some things that people in the story Fever 1793 think caused yellow fever?

In chapter 8, Mr. Carris reads the mayor's orders from a broadsheet newspaper. From these orders we can infer some of the factors which people in the story think of as possible causes of yellow fever.
The first order is that everybody "should avoid those that are infected." The implication here is that people think that yellow fever is contagious via direct contact with those already infected. This thought is confirmed by the second order, which states that "The homes of the sick should be marked." Presumably, this is to reduce the risk of direct contact with an infectious host body.
Order number nine states that "All persons should avoid being in . . . drafts." The implication here is that yellow fever can be carried in the air, and thus can be passed from one person to another not only through direct contract but also by the two people simply being in the same vicinity.
Another cause of yellow fever implied by the mayor's orders is uncleanliness. Order seven states that "The streets and wharves must be kept clean." This implies that yellow fever might spread through dirt.
Orders number eight and eleven, that people should "avoid fatigue of the body and mind" and "consume alcohol in moderation," suggest that people in the story also think that yellow fever can be more easily caught if one is careless about one's physical or mental health—in other words, if one's immune system is weaker than usual or if one is less able intellectually to take careful precautions.