Diagnostic Case Study:

Late summer 2012, a 60-year-old man was admitted in a hospital complaining about headache, high fever, neck stiffness, and muscle weakness. The man appeared confused and disoriented. History indicated that he was fishing with friends in an isolated swamp area in the southwest of Louisiana about two weeks previously. Samples of blood and cerebrospinal fluid (CSF) were sent to a clinical laboratory. The report indicated that the patient was suffering from West Nile virus. 

Questions:

1. How did this man most likely become infected with West Nile virus (WNV)?

2. Why are humans considered incidental (accidental or dead-end) hosts of WNV?

3. Why did the physicians in the hospital make the decision to send samples of blood and CSF from this patient to the clinical laboratory?

4. Which serological test is frequently used to detect WNV and what is the limitation of this test?

5. Due to the limitation of serological testing, real-time quantitative polymerase chain reaction (RTQ-PCR or qPCR) is used routinely for the diagnosis of WNV. How does this method work and how can it help estimate the number of virus particles present in collected body samples?

6. Why is West Nile fever considered a new and emerging infectious disease in the United States?