From the LA Times - West Nile virus in California.
...Morris, 55, did not know she’d been bitten, but her body did. A small red welt rose on her skin, an everyday allergic reaction to the foreign proteins in the bug’s saliva.
For the last 11 months, health officials in the United States have focused on the spread of the Zika virus from Brazil, yet epidemiologists and vector control experts in California continue to be alarmed by the steady presence of the West Nile virus in Los Angeles and Orange counties. ...
...Inside Morris’ spinal fluid, the virus continued to replicate, destroying neurons as it burst out of the cells it entered. Her body began to mount a counterattack as dangerous as the assault.
The spleen, the immune system’s command center, began flooding her body with white corpuscles, lymphocytes. One class, B-cells, prepare a long-term defense, producing antibodies that can swarm the virus and prevent it from commandeering other cells, a process that takes up to 10 days. T-cells take more immediate action, swarming the sites of infection. ...