New York Times - The outbreak began so slowly that no one in Dallas perceived it at first. In June 2012, a trickle of people began showing up in emergency rooms broiling with fever, complaining that their necks were stiff and that bright lights hurt their eyes. The numbers were initially small; but by the middle of July, there were more than 50 victims each week, slumping in doctors' offices or carried into hospitals comatose or paralyzed from inflammation in their brains. In early August, after nine people died, Dallas County declared a state of emergency: It was caught in an epidemic of what turned out to be West Nile virus, the worst ever experienced by a city in the United States. By the end of the year, 1,162 people had tested positive for the mosquito-borne virus; 216 had become sick enough to be hospitalized; and 19 were dead.
If the impact of climate change on mosquitoes and the diseases they carry were predictable, anticipating what comes next might be simple. It is not. The perturbations that cause a moist early spring like the one Dallas had in 2012, favoring mosquito reproduction, can equally cause devastating floods - like the wall of water that swept through central Texas in May 2015 and killed 11 people - that will scour mosquito eggs from wherever they have been laid. Warming temperatures that allow mosquitoes to move north into new territory may also make their current territory inhospitable. In 2012, researchers at Texas Tech University estimated that in Chicago, rising temperatures would expand the length of the season for the mosquito that carries dengue - but in Atlanta and Lubbock, Texas Tech's home turf, summers would become so hot and dry that the risk of transmission would shift to spring and fall, when residents would not be on guard. The unpredictability will increase the challenge of preparing for diseases whose incidence will also increase.