With two human West Nile cases already confirmed, and near-perfect weather conditions for mosquitoes, it's no time to be blase about the dangerous virus, experts warn.

"The numbers are definitely creeping up," said Tony Stilwell, operations manager for Colorado Mosquito Control, which has contracts with most Front Range cities to spray for mosquitoes.

The flood-water mosquitoes, those that like the ebb and flow of water for egg-hatching, have passed their peak, and now comes the ascension of culex tarsalis, the species that carries West Nile, Stilwell said.

Culex tarsalis love warm, dry weather, which the Front Range has seen plenty of. By the end of July, officials should have a good grasp on what kind of season to expect, but Stilwell noted that some states have seen a bump four years after the worst year. In 2003, Colorado led the nation in West Nile deaths with 63.

The two cases so far have been in Weld and Logan counties, but West Nile-carrying mosquitoes are rising on the whole Front Range, he said.

Public health officials urged Coloradans venturing outdoors this summer to wear mosquito repellent with DEET, avoid mosquito areas, especially at dawn and dusk, rid their backyards of standing water, fix window screens and wear long shirts and pants outside when mosquitoes are active.