The Contra Costa Mosquito and Vector Control District announced Friday that four more birds have recently tested positive for West Nile virus.
Two of the infected birds came from Brentwood, one from Walnut Creek and one from Oakley, according to control district officials.
The district is urging residents to report all dead birds by calling 1-877-WNV-BIRD.
So far in 2014, 19 groups of mosquitoes, 13 chickens and 35 dead birds have tested positive for the virus, according to the district.
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