This brings the total number of birds that have tested positive in San Luis Obispo County to nine. As of September 14, 2004, 523 West Nile Virus human infections have been reported in California this year.

Fifty of the 523 WNV infections were initially detected in asymptomatic individuals through screening done at blood banks. Five of these individuals later became symptomatic.

Of the 478 WNV cases with symptoms, 172 are classified as West Nile fever cases, 162 are classified as West Nile neuroinvasive disease, and 144 are of unknown status.

The median age for all cases where data was available is 52 years of age. To date, there have been no confirmed human cases of WNV in San Luis Obispo County.

"West Nile Virus (WNV) is present in San Luis Obispo County. The best way to avoid the disease is to reduce exposure to and eliminate breeding grounds for mosquitoes."

San Luis Obispo County citizens can protect themselves from mosquito bites by avoiding outdoor activities during mosquito-prone times (e.g. between dusk and dawn), wearing long sleeves and long pants when outdoors, and using a repellent containing DEET. Follow the label directions when using any repellent.

Also, it is important to wear gloves when handling any dead bird or mammal. Be sure to look around your home and property and empty any standing water fro

It is also important to check irrigation systems for over-watering that can lead to puddles and pools of standing water. Mosquitoes are able to breed in very small quantities of water.

The virus can, in rare cases, cause a form of encephalitis (inflammation of the brain) or meningitis (inflammation of the tissue layers covering the brain and spinal cord).

It is important to note that only about one in 150 people infected with West Nile Virus will become severely ill. There is no evidence of horses or birds transmitting West Nile Virus directly to humans, and it is not typically spread from person to person. Rarely, it can be transmitted via blood transfusions or organ transplantation. New blood bank procedures are now screening for WNV.

Most animals will recover from the virus; however, horse death rates may be as high as 33%. Some animals will show symptoms from mild illness to death when infected with the virus. Horses will show symptoms of listlessness, staggering, fever and weakness when infected.

If you think your animal has the West Nile Virus, contact your veterinarian. There is a licensed vaccine available for horses; data to date indicate that this vaccine is safe and shows some effectiveness. Horse owners should consult with their veterinarian to get more information about this vaccine.

There is no commercially available vaccine for any other type of animal or for humans. However, an injectable bird vaccine is being developed for the purpose of vaccinating wild birds.