A dead bird found in Blackhawk last weekend tested positive for West Nile virus, marking the first virus activity documented in the San Ramon Valley this year, Contra Costa Mosquito and Vector Control District officials announced on Thursday.
The dead American crow was discovered near the intersection of Deer Meadow and Live Oak drives last Sunday, district officials said.
All of the other virus activity in Contra Costa so far this year has occurred in east county, including a dead bird in Oakley and mosquito groups in Holland Tract and Byron that all tested positive in the past week, according to district officials.
"The dead bird in Blackhawk is the first detection of West Nile virus in that area this year," said Steve Schutz, Ph.D., scientific program manager with the district.
"To date this year, we had only seen West Nile virus activity in east county, which is typical because the weather is hotter there,” he added. “And while activity is increasing, it pales in comparison to other Northern California areas that are experiencing, in some cases, unprecedented West Nile virus activity, such as in the San Joaquin and Sacramento areas."
No human cases have been reported in Contra Costa County to date this year.
Most cases of the virus in humans are mild and include symptoms such as fever, headache, tiredness, body aches and swollen lymph glands, according to district officials. Severe cases of West Nile virus can be fatal.
The most recent Contra Costa County human fatalities from the virus occurred in 2006, when two people died, officials said.
Birds are the reservoir for West Nile virus, which can be transmitted to humans via mosquitoes.
The two species of mosquitoes in the county capable of transmitting the virus prefer to feed on birds, but people can become infected when a mosquito bites an infected bird and then a person, district officials said.
The district preaches prevention, encouraging people to wear mosquito repellents, avoid going outside at dawn or dusk when mosquitoes are often present, dump or drain standing water where mosquitoes could lay their eggs, and report dead birds and neglected swimming pools.
District officials are planning to conduct preventative fogging for adult mosquitoes Friday morning at the Holland Tract Marina, Byron and agricultural lands east of Discovery Bay, weather permitting.
For more information, visit the district website.