Fire is both fact and symbol here: it started out as a comfort (with Grandpa), became a necessity (with Liz and Jenna), and now is its own source of danger, as it tears down Brownlee and becomes a metaphor for the sting of the Brazilian bugs. The narrator’s government job has similarly switched symbolic meaning: whereas he was hated as an evacuator, he is now loved to a “sick[ening]” degree. It is also worth noting that many citizens committed arson, maybe as protest or out of boredom.