Three cases of West Nile virus were found last week in horses, the first reported equine cases this year, according to the state Department of Agriculture.

The horses were from Jefferson, Lauderdale and Tipton counties.

The virus claimed its first human victim this year in Shelby County on Sept. 13. The state has confirmed the virus this year in mosquitoes and birds throughout the state.

The virus is spread through the bite of infected mosquitoes. While usually not serious in humans, it can lead to encephalitis, a potentially deadly inflammation of the brain.