As West Nile spreads across California, a nondescript laboratory on the University of California at Davis campus has become the unlikely command post in the fight against the virus.

Doctors and lab technicians test thousands of birds, insects and animals weekly that are shipped to the university from around the state by vector control officials who suspect West Nile is in their areas.

The results of these tests have become crucial in following the path of the virus, which has moved steadily in the last two months into Los Angeles County and north into the Central Valley and the San Francisco Bay area. The tests also can help pinpoint clusters where West Nile is prevalent, giving local officials ideas on where to target spraying.

The work is not for the squeamish.

Lab employees rip apart dead birds. They crush mosquitoes into a pulp before testing them.

On a recent day, a cow carcass, tongue hanging from its mouth, lay on the floor awaiting dissection. A dead horse was nearby. A few feet away, dozens of dead birds, individually packaged in plastic bags, were in line to be gutted.

Since West Nile began its spread into urban California in the spring, the lab has been working nonstop.

"It's been crazy -- April, May, June, July, August," said Marzieh Shafii, a staff research associate, noting that the lab tests hundreds of birds and about 800 mosquito pools -- which equals about 40,000 mosquitoes -- a week.

Local health and vector control officials say the lab's efforts have made a huge difference in the fight against West Nile, which has killed at least 10 people in California and infected more than 340. The virus is spread to humans by mosquitoes, which in turn get it from birds.

"It's extremely important," said Brit Oiulfstad, a veterinarian with the Los Angeles County Department of Health Services. "It's an essential clearinghouse, a centralized test we can all rely on."

The work is done in various areas of the leafy UC Davis campus, near Sacramento. The dead birds, for example, are tested at the School of Veterinary Medicine. Genes from bird tissue and mosquito pools are whisked over to the university's Center for Vectorborne Diseases lab, located in trailers off a dirt road.

At this lab, a machine extracts cellular coding from the tissue from animals and mosquitoes to determine if West Nile is present.

Then the test results are sent to the state health department, which distributes them to local health departments and vector control agencies. The information is used to determine where the virus is and how local health officials can educate the public on preventing its spread.

The entire process -- from a city resident calling in a dead bird to the state receiving the results -- usually takes about 10 days, health officials said.

"A bird doesn't drop out of the sky and then it's tested and the reports go out the next day," said Barbara Cahoon-Young, a lab manager. "There's a lot that goes on behind the scenes to make sure that it all runs smoothly."

After vector control workers collect dead birds, they are double-wrapped in plastic sandwich bags, then packed in foam or cardboard boxes, said Leslie Woods, a veterinary pathologist and professor at the university's veterinary school. United Parcel Service is used to deliver the boxes to the lab.

On a recent day, the UPS truck arrived at 10:10 a.m., and the driver unloaded eight boxes, a small number, Woods said.

Jacquelyn Parker, a staff research associate, said they never know how many birds they will get.

"It's usually a surprise when we open the box," Parker said.

Each box, marked "WNV Surv," meaning West Nile virus surveillance, includes at least one bird and at least one cold pack, usually a frozen two-liter soda bottle or can.

In the West Nile room, intern Ian Holser cuts open the cardboard boxes. Among the more than 20 birds they received is a mourning dove from San Luis Obispo County and a Western scrub jay from San Benito County.

Holser carries the birds to the biological safety hood in a corner of the small room. The hood resembles a desk with a glass partition that extends down to chest level, separating the researcher's face from the specimens, thus keeping any infectious agents behind a barrier.

In less than a minute, Holser pulls on purple latex gloves, removes the bird from the bag, squirts water to moisten the feathers, cuts the chest with scissors and pinches off a BB-size specimen of kidney.

He delicately drops the specimen in a vial marked with the bird's identification number, then throws the carcass into a red biohazard bag. The bag is placed in a cooler until it can be incinerated.

After Holser places the birds' specimens in separate vials, he puts them in a cooler, which will be taken to the second lab for testing.

At this point, all specimens -- whether bird tissue or mosquitoes -- are ground to a pulp by the robotic 6700 Automated Nucleic Acid Workstation. It shakes the vials until their contents are mashed, making it possible to extract a clear genetic liquid.

"The nice thing about the robot is that we can process 86 mosquito pool samples at one time," Shafii said.

The next step is the TaqMan, a machine that tests the material to determine whether it contains West Nile virus and charts the results on a computer.

The results are sent to the state health department, whose officials announce to the public and local health and vector control agencies the latest information.

Based on data from UC Davis, local vector control agencies have been able to warn the public about clusters of West Nile in places such as Colton and Fontana, east of Los Angeles. In recent weeks, the data have helped officials track the virus as it has moved north from Los Angeles into the Central Valley and the San Francisco Bay area.

About 20 percent of people infected with the virus experience flulike symptoms. In about one in 150, the symptoms progress to encephalitis, a swelling of part of the brain. Fewer than 1 percent of those infected die from the virus.

The work at the labs might seem mundane, but lab officials say they get a charge from the fact that they are helping protect the public.

"The whole dynamic is very exciting," Cahoon-Young said.

Mosquitoes collected from Harbor City, Calif., by Jennifer Wilson have been paralyzed so they can be tested for West Nile Virus.