Two people from east Contra Costa County have tested positive for West Nile virus, the county Mosquito and Vector Control District announced. The adults were likely infected by virus-carrying mosquitoes in late September.
A dead American crow found in Alamo has also tested positive for the virus. The bird was found near Golden Grass Drive and Stone Valley Road.
"This year we have received five reports of people who have tested positive for West Nile virus. Through patient interviews, it is likely only two were infected locally. The other three people were determined to have been infected outside of Contra Costa County," said Deborah Bass, spokeswoman for the district. "It's very important to remember that the majority of West Nile virus cases are not reported. In fact, based on data from the CDC, we estimate that in Contra Costa County up to 280 people were affected by the virus last year, they just didn't know it or it wasn't reported."
Birds are the reservoir for West Nile virus. The two species of mosquitoes in Contra Costa County capable of transmitting the virus prefer to feed on birds; however, people can become infected when a mosquito bites an infected bird and then a person.
West Nile virus symptoms of the mild form include fever, headache, tiredness, body aches and swollen lymph glands. While the illness can last only a few days, even healthy people have reported being sick for several weeks. West Nile virus of the severe form can be fatal.
The public is encouraged to keep mosquitoes at bay by dumping or draining standing water, wearing mosquito repellant and avoiding being
outside when mosquitoes are most likely to be present; typically at dawn or dusk.
Since 2005, 49 people in Contra Costa County have been diagnosed with West Nile virus. In 2006, two people died from the disease. In 2013, a total of five people, 13 groups of mosquitoes, 68 dead birds and seven chickens have tested positive for the virus.