Family life is, at least at the beginning of the novel, a defining force in Matilda Cook's life. Her mother is the sole authority figure she must obey, and her grandfather provides her with an extensive education about the ins and outs of soldiering (Revolutionary War style, of course). As the fever hits, though, her family members disappear one by one. Matilda must figure out who exactly she is, even when she has no one but herself to depend on.
For Matilda, food is a source of comfort and a symbol of home. It's strongly associated with the life of the coffeehouse and, most specifically, with Eliza (who is, by the way, a wonderful cook). When there's not enough food around, you can bet that something is going very, very wrong. Matilda will struggle to forage for and cook her own food, for example, in Chapter 18. She also dreams about food at the beginning of Chapter 19.
Characters in the novel are often defined through their geographical location: do they live in the city or do they live in the country? The two places represent, at least in Matilda's mind, very different ways of life. The city is a place of thriving commerce, social circulation, news, and excitement. The country? Well, it's a place, as Matilda tells us, for "slopping pigs" (8.68). As the fever epidemic rages, though, Matilda will find out that death really doesn't make such geographical distinctions. Nowhere is completely safe from the disease.