After negative tests for several viruses, which viral test should be done in a young female with a sore throat and lymphadenopathy?

In a young female presenting with a sore throat and lymphadenopathy, the most appropriate viral test to perform after negative tests for several other viruses is for Epstein-Barr virus (EBV). This is because EBV is typically associated with infectious mononucleosis, which is characterized by symptoms such as sore throat, swollen lymph nodes, fatigue, and sometimes fever. The clinical presentation of sore throat and lymphadenopathy strongly aligns with this condition.

Herpes simplex virus primarily causes oral and genital lesions and may not typically present with generalized lymphadenopathy like EBV does. Rubella is often associated with a rash and mild respiratory symptoms but is less likely to present solely with sore throat and lymphadenopathy at this age. Lastly, while West Nile virus can lead to neurological symptoms and a variety of systemic issues, it wouldn't usually be the first consideration in the presence of classic mononucleosis symptoms. Therefore, testing for Epstein-Barr virus would be the most logical next step in this clinical scenario.