Last updateWed, 20 Sep 2017 9am


West Nile carrier identified in LA

Photo By: Ellie Van Houtte/Town Crier
Photo Ellie Van Houtte/Town Crier

Santa Clara County Vector Control technician Caroline Dunkelberger inspects a virus surveillance trap in a San Jose neighborhood. When a bird tests positive for West Nile virus, the county places traps to collect mosquitoes for lab testing.

After a crow from Los Altos tested positive for West Nile virus July 20, Santa Clara County Vector Control officials boosted efforts to monitor the mosquito population.

Mosquitoes can become infected with West Nile virus by feeding on American crows, Western scrub-jays and other birds that carry elevated concentrations of the virus in their blood streams, according to vector control District Manager Russ Parman.

After identifying the infected bird in Los Altos, vector control placed 40 mosquito traps in locations within a 1-mile radius of where the bird was found to trace, track and predict the spread of the virus.

The district tests the genetic materials of the collected mosquito samples to determine whether West Nile virus is present. If a mosquito tests positive, the agency notifies residents and begins chemical fogging to eradicate the virus.

Despite the incidence of West Nile in Los Altos, Parman said there is no need for alarm.

“This is a record low for this time of the year,” he said.

Parman said that although the numbers remain low, an additional eight birds tested positive for the virus in Santa Clara County, and several investigations are under way. Major outbreaks of the virus typically last two weeks, he said, but hot spots in San Jose stayed active for six weeks in 2011 – even with extensive control measures.

It’s too early to predict whether West Nile virus will spread to humans, Parman said. Although county vector control has yet to identify any human cases of West Nile virus this year, 16 cases were diagnosed between 2003 and 2011. The Centers for Disease Control and Prevention estimates that 80 percent of those infected by West Nile virus are asymptomatic and may not even realize they were infected. Others experience severe fever and potentially fatal neuroinvasive complications. Between 2003 and 2011, the California Department of Public Health recorded 110 deaths in the state related to the virus.

Suppressing mosquito populations and educating the public on bite prevention is critical to slowing the spread of infection to humans, Parman said. Most people heed the warnings to use insect repellant and avoid the outdoors at dusk and dawn during the warm summer months, he added.

However, the ongoing maintenance of stagnant pools of water, whether children’s pools, dirty gutters or puddles filled with hose or sprinkler runoff, is frequently overlooked. During the recent increase in home foreclosures, vector control used aerial surveillance to document more than 1,600 abandoned or neglected swimming pools – ideal breeding environments for mosquitoes.

Parman said that predicting an outbreak is difficult, but he encouraged the public to assist by reporting any suspicious dead birds or squirrels online at www.westnile.ca.gov or by calling (877) 968-2473.

Although 2012 is so far a quiet year for the virus, other diseases carried by birds remain a concern.

“We anticipate more subtropical diseases moving forward,” Parman said.

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