A dead bird in Danville tested positive for West Nile virus earlier this month, the Contra Costa Mosquito and Vector Control District announced on Thursday
The American crow discovered on Aug. 3 at the intersection of Brookside and Greenbrook drives is so far the only San Ramon Valley virus detection of the year, according to district officials.
However, three dead birds from nearby Walnut Creek also tested positive for the virus earlier this year.
"We monitor virus in insects and animals because it provides an indication that people are at risk of becoming infected," said Steve Schutz, Ph.D., the district's scientific programs manager. "Everyone should take all the recommended precautions to avoid mosquito bites. While the majority of people who become infected with West Nile virus do not experience symptoms, some develop West Nile fever or encephalitis, which can lead to paralysis, long-term disability or even death."
Extra surveillance and mosquito control is being conducted in the areas where the virus was detected.
Statewide for 2017, 171 dead birds, 22 humans, 1,814 mosquitoes and 58 sentinel chickens (chickens specifically used to detect the virus) have so far tested positive for West Nile.
As of Aug. 8, no humans had died from the virus. Last year, 19 of the reported 442 human cases were fatal, according to the California Department of Public Health website.
According to district officials, 56 people in Contra Costa County have been diagnosed with West Nile virus since 2005, with two fatalities occurring in 2006.
In humans, most cases of the virus are mild and include symptoms like fever, headache, tiredness, body aches and swollen lymph glands, officials said. Severe West Nile virus cases can be fatal.
Birds are often the first sign of disease transmission: they're the reservoir for West Nile virus, which can be transmitted to humans via mosquitoes. So local officials recommend immediately reporting sightings of dead birds or neglected swimming pools where mosquitoes could populate.
The two species of mosquitoes in Contra Costa 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.
In order to reduce the risk of contracting mosquito-borne diseases, officials recommend that residents dump or drain standing water, use insect repellents, avoid going outside when mosquitoes are typically out (generally dawn and dusk), maintain neglected swimming pools and report dead birds to the state hotline at 1-877-968-2473 or at the California Department of Public Health website.
For more information, visit the district's website.