A 49-year-old woman developed a high fever five days ago, along with a retro-orbital headache, body aches, anorexia, and intermittent nausea and vomiting. The fever subsided last night, but the other symptoms still persist. She had returned home just one week ago, following a three-week trip to Sri Lanka. Her medical and surgical histories are unremarkable, she does not smoke, and only drinks socially. There is no history of recreational drug abuse or unsafe sex.