California Governor Arnold Schwarzenegger has declared a state of emergency in Kern, Colusa, and San Joaquin counties after West Nile virus killed four people in the state and has infected 60 others.

Five horses in three counties have tested positive for West Nile virus, which has been confirmed as active in 42 counties in California.

“I’m taking action to help the counties hit hardest by West Nile virus,” Governor Schwarzenegger said. “My proclamation makes financial assistance available to the local vector control districts and directs state agencies to take proactive measures to protect Californians from further spread of this deadly virus. I will continue to ensure our local agencies have whatever resources they need to fight the spread of this disease.”

There was one new confirmed equine case of West Nile virus last week.

Horses infected with the potentially lethal virus often demonstrate signs of West Nile virus that may include stumbling, circling, hind leg weakness, inability to stand, muscle tremors. Approximately one-third of horses infected with the virus die or are euthanized.

West Nile virus is most often spread by the bite of an infected mosquito.

Mosquitoes become infected when they feed on infected birds and become West Nile virus carriers. Infected mosquitoes can then spread the virus to humans and other animals when they bite.

A vaccine to prevent West Nile virus is available for horses. Horse owners should consult with a veterinarian about the vaccine and other vaccines against mosquito-borne viruses.

West Nile virus is not spread through casual contact with the virus or by breathing in the virus.

Humans typically develop symptoms, such as fever, headache, neck stiffness, stupor, disorientation, tremors convulsions, muscle weakness, vision loss, and paralysis from three to14 days after they are bitten by an infected mosquito.

There is no specific treatment for West Nile virus infection, however in milder cases symptoms such as fever and aches and pains often pass on their own.

“Please rest assured that I will make available as much funding as immediately needed to combat this virus at a local level,” Schwarzenegger said in a letter to California State Senator Dean Florez, (D-Bakersfield), who requested a minimum of $48-million in state funding to fight the epidemic, the Bakersfield Californian reported.