"A horse stabled near the town of Sonoma has tested positive for West Nile virus, becoming the first equine case in Sonoma County this year, county health and vector control officials said Friday.

The Sonoma horse is the second horse in California this year to be infected with the mosquito-transmitted virus, which is often fatal. Health officials fear widespread West Nile infections this year in birds, horses and humans.

"The West Nile virus arrived in Sonoma County early this year and there is a high probability that we will see many infections, including in humans," Dr. Leigh Hall, Sonoma County's deputy public health officer, said Friday."