Atlanta ? West Nile virus activity has again doubled, now affecting more than 1,400 people in the United States, federal officials said Wednesday.

Thirty-four states reported a total of 1,442 cases and 21 deaths, the Centers for Disease Control and Prevention said. Last week, the agency reported 715 cases and 14 deaths.

Colorado and the central United States continue to be the hardest hit. Colorado’s 635 human cases lead the country, followed by 204 cases in South Dakota, 190 in Nebraska and 106 in Texas.