Apparently some doctors “have to be prompted” to test:

Lisa, who declined to give her last name for privacy reasons, said her physician thought her symptoms were typical of the virus that causes mononucleosis, and only tested for West Nile when she prompted him to do so.

Dr. Henry Lim, who operates a family practice on the Mountain, said he did not initially recognize the symptoms despite having seen a case of West Nile virus a couple years ago.

“It’s a very difficult diagnosis to make. You don’t want to test everybody who comes in with a cold,” Lim said in a telephone interview. “Other doctors are missing it too.”