“I’m sending you a patient.” The voice on the phone belonged to Fabio Giron, a critical-care specialist and one of the smartest doctors I know. “Twenty-nine-year-old guy, headache, photophobia, fevers off and on for two weeks. Trouble urinating. Ataxic gait.” “Bizarre,” I replied. “Start with a head CT and spinal tap?” “Definitely. I can’t figure out if it’s viral meningitis or maybe a brain abscess,” Fabio said. Th...