As West Nile virus spreads on the East Coast, UC Davis scientists have found that the abundant house finch is a good host for two related viruses found in California. West Nile virus was first detected in the United States in 1999, when seven people died and 55 were hospitalized. Humans are infected when bitten by a mosquito that has previously bitten an infected bird. The virus does not spread directly between humans or between birds and humans. Western equine encephalomyelitis and Saint Louis encephalitis cause are transmitted in the same fashion. Infections in humans are usually mild or have no symptoms, but can be severe or fatal in infants and the elderly. No human cases of Saint Louis encephalitis or western equine encephalomyelitis have been reported in the state since 1997, according to data from the California Department of Health Services. "Saint Louis encephalitis virus may be a good model for how West Nile virus could spread in California," said UC Davis entomologist William Reisen. The results will be presented at the annual meeting of the Mosquito and Vector Control Association of California in Silverado, Calif., Jan. 21-24. More of the bird species tested became infectious with western equine encephalomyelitis than with Saint Louis encephalitis, said Reisen. House finches were particularly susceptible to both viruses. Because house finches are common year-round resident birds, they could be important in sustaining the viruses in California, said Reisen. Species such as brown-headed cowbirds, scrubjays, robins and quail were poor hosts. House finches, white-crowned sparrows and song sparrows were susceptible to Saint Louis encephalitis. Because white-crowned sparrows are winter visitors to California, they are not likely to be important reservoirs of the virus, said Reisen. The research was supported by grants from the National Institutes of Health, the UC Mosquito Research Program and the Kern and Coachella mosquito and vector control districts. UC Davis collaborates with other UC campuses, the California Department of Health Services, and local mosquito and vector control agencies to monitor mosquito-transmitted viruses.