San Gabriel Valley officials are sounding the alarm on the West Nile virus after the latest case was discovered last week in a chicken flock.
The infected flock was located in Claremont, and it was the latest in a series of West Nile virus cases reported in the region. Last month, positive tests were confirmed in samples taken from mosquitoes in the city of Arcadia and from three chicken flocks in Arcadia, Irwindale and Monterey Park, according to the San Gabriel Valley Mosquito & Vector Control District.
San Gabriel Valley officials said they are "very concerned" because it is possible that more than 1,000 cases of the virus in Los Angeles County this year have not been tested and reported.
"This level of underreporting leaves residents with the mistaken impression that WNV is not a big problem so they do not take these warnings seriously," Vector Control District Manager Kenn Fujioka said in a statement. "Any patient or their family members would testify that getting sick from West Nile virus is not a trivial issue."
West Nile is spread through mosquitoes, which get the virus by biting infected birds. The vector control district maintains chickens throughout L.A. County to test for and track the virus. August and September are typically peak months for transmission.
Most cases cause mild or no symptoms in humans, but rare cases can lead to serious illness or death.
There have been 74 human infections reported this year, according to the Los Angeles County Department of Public Health. Of those, 46 were listed as the more severe West Nile neuroinvasive disease.
The San Gabriel Valley Mosquito & Vector Control District urged residents to take precautions against mosquito bites, "as transmission is expected to continue throughout the summer and fall months."
Earlier this month, West Nile activity forced the indefinite closure of the Madrona Marsh, a 10-acre preserve in Torrance popular with bird-watchers and other recreational users.
To guard against mosquito bites, officials recommended wearing long sleeves, pants and repellent, and making sure doors and windows have screens. They also suggested avoiding outdoor activity from dusk to dawn, when mosquitoes are most active.