Three viruses that can make you sick have been detected in Washoe County -- mosquitoes are suspected of carrying all of them.
Mosquitoes in Damonte Ranch and Bella Vista Ranch have tested positive for West Nile Virus.
The bugs are also believed to be carrying two forms of encephalitis.
If the viruses are transmitted by a bite, they can make humans ill.
The county has been spraying to reduce the mosquito carriers, and will do so again Thursday.
The Washoe County District Health Department is also reminding people to wear long-sleeved shirts at dusk and dawn when mosquitoes are most-active.
The severe form of West Nile Virus can lead to death.
Thus far, health officials report two human cases of West Nile in Nevada this year-- one in Pershing County and the other in Clark.