The number of U.S. cases of West Nile virus climbed by nearly a third in the latest week as the spread of mosquito-borne disease accelerated and threatened to make the 2012 outbreak among the most severe on record, government figures showed on Wednesday according to Reuters. So far this year, 2,636 cases have been reported to federal health officials, up from 1,993 reported the week before, the Centers for Disease Control and Prevention said in its weekly update of outbreak data. A total of 118 people have died from the disease, compared with 87 reported one week ago. The disease has been reported in people, birds or mosquitoes in 48 U.S. states, so far absent only in Alaska and Hawaii. Texas accounted for about 40 percent of all human cases. Two-thirds of the cases have cropped up in six states - Texas, Louisiana, South Dakota, Mississippi, Michigan and Oklahoma. Of the cases reported to the CDC this year, 1,405, or 53 percent, are of the severe neuroinvasive form of the disease, which can lead to meningitis and encephalitis. The milder form of the disease causes flu-like symptoms and is rarely lethal. West Nile outbreaks tend to be unpredictable. Hot temperatures, rainfall amounts and ecological factors such as the bird and mosquito populations have to align just right to trigger an outbreak like the one this year. The CDC said the number of cases this year is the highest reported to federal health officials through the second week in September since 2003, the worst year on record. The disease is thought to have originated in Africa and was first detected in New York City in 1999. This year's outbreak already is more than three times the size of last year's, when 712 cases were reported nationally, with 43 deaths. -- SPA
