Six mosquito samples and one dead bird have tested positive for West Nile virus this week in Placer County.

The mosquito samples were collected from sites along the county’s western border, from as far south as the north Elverta area, and as far north as Lincoln. The dead bird was collected from Rocklin.

Mosquito numbers have also increased in the past week, most likely from sustained higher temperatures.

“We are concerned that the timing of this increase in West Nile virus activity comes right before a long holiday weekend, when people are more likely to be spending a lot of time outdoors, especially during the dusk and evening hours,” Joel Buettner, Placer Mosquito and Vector Control District, said in a press release.

The district is planning aerial treatments tonight and ground-based treatments Thursday morning for adult mosquitoes.