The term "Roman Fever" is an old one for malaria. The title is a form of verbal irony because "Roman Fever" has a dual meaning: on the surface, it means malaria but it also symbolizes Alida's raging, disease-like jealousy of Grace Ansley that she has harbored for all of these years. This story is loaded with irony. Alida Slade has had, in some sense, what appears to be a more successful life than her "friend" and she tries to convince herself she has no reason to be jealous. With some good foreshadowing, the author leads us to believe that Alida does not really believe this, deep down, that there is some reason why she is jealous of Grace. Grace's daughter, Barbara, for example, is much more vivacious and lively than Alida's daughter. The jealously that she has harbored against Grace for all of these years has wound up, in the end, destroying her, like a disease, not her friend.
We find out that Alida tricked Grace into going to the Colosseum to meet Delphin (who was Alida's fiance at the time) by writing a phony letter that was supposed to be from him. She was so jealous that her reason was affected, however, because she did not count on Grace answering the letter, which she did. When Delphin got the letter, he went to the Colosseum to meet Grace because he obviously was in love with her, just as Alida had suspected.
The irony is that while Alida thought she was going to make Grace sick by being out late at night in the cold, she really made herself sick, not only with her jealousy, but she caused her fiance to meet Grace, make love, and have a child with her. Barbara is really the child of Delphin. All of these years, Alida and Delphin have lived across the street from Grace and her husband Horace, not knowing that Barbara was Delphin's daughter. Alida cannot understand how the unremarkable Grace and even more unremarkable husband, Horace, could have had such a lively, beautiful daughter. Now she knows.
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