Cases of West Nile virus (WNV) infection are being seen in the largest numbers since the disease first was detected in the United States in 1999, according to an Aug. 14 update from the CDC.

So far this year, 43 states have reported WNV infections in people, birds or mosquitoes, the agency notes.

“A total of 693 cases of West Nile virus disease in people, including 26 deaths, have been reported,” says the CDC. “Of these, 406 (59 percent) were classified as neuroinvasive disease (such as meningitis or encephalitis) and 287 (41 percent) were classified as non-neuroinvasive disease.”

It’s worth noting that not only is that case total the highest reported to the CDC since 1999, 80 percent of those cases come from only six states: Texas, Mississippi, Louisiana, Oklahoma, South Dakota and California. Moreover, almost half of all cases — including nine deaths — were reported from Texas, prompting one judge to declare a state of emergency in Dallas. In response, the state recently began spraying insecticide from crop-dusting planes in certain areas to kill WNV-infected mosquitoes.