Flor Arely Sánchez had been in bed with a fever and pains throughout her body for three days when a July thunderstorm broke over the mountainside. She got nervous when bolts of light flashed in the sky. Lightning strikes the San Julián region of western El Salvador several times a year, and her neighbors fear storms more than they fear the march of diseases — first dengue, then chikungunya, now Zika. Flor worried about a lot of things, since she was pregnant.
Late in the afternoon, when the pains had somewhat eased, Flor thought she might go to a dammed-up…