Fifteen dead birds testing positive for West Nile virus have been found in Santa Clara County already this year, said Russ Parman, the acting district manager for the Santa Clara County Vector Control District. One of these birds was found in Mountain View, along with one in south Palo Alto and another in northern Los Altos.
"Spring rains have left a lot more water for mosquitoes to breed in," Parman said. "It's kind of a weird year in that we're up to 15 positive birds now, compared to 14 total last year."
On Friday, June 11, Vector Control conducted its second aerial survey of the year. The operation covered 80 miles in the southwest San Jose-Cupertino-Campbell area in search of neglected pools, which are a breeding ground for mosquitoes. Parman said state risk models have pinpointed this area as particularly active, which indicates a higher risk of human cases. District officials will be monitoring this area extremely closely.
The district does mosquito trapping around dead birds, and if infected mosquitoes are found, it initiates "fogging mode," which Parman said is an attempt to knock down the adult mosquito population.
Dead birds are an important indicator of West Nile virus. Crows, which Parman says are 95 percent susceptible to West Nile, can hugely amplify the virus within a mosquito population in a sort of positive feedback loop. A dead bird releases the virus into its blood stream and then becomes a tasty meal for adult mosquitoes, which go on to infect other birds and potentially humans.
So far this year, there have been no human cases reported in California. The disease causes severe flu-like symptoms in those who are particularly susceptible, such as people with compromised immune systems, diabetics, or people over 50. But this is actually a relatively small percentage of cases, Parman said.
"Eighty percent of people who get the virus never know they have it," he said.
The most important thing people can do is to properly maintain pools and eliminate other standing water sources, Parman said.
"Chlorinate and keep it circulating," Parman recommends to pool owners. If a pool is going unused, drain it.
If residents can't afford pool maintenance, district employees can conduct an inspection and treat the pool with mosquito fish if necessary. Households with at-risk pools identified by the aerial survey will be contacted.
Parman said that Mountain View will most likely be surveyed in the district's third aerial sweep of the year, which will take place some time in July. But as the weather heats up, many sources of standing water will dry up, reducing the mosquito population.
"Personally, I'm hoping this thing tapers off a bit," Parman said.
As of now, it is unclear how the virus' presence will pan out over the coming months.
"Either the virus will amplify or this peak will fizzle out," Parman said. "Only time will tell."
Contact the Vector Control District if you are bothered by mosquitoes or know of a potential mosquito-breeding source at (408) 918-4770. Report dead birds to the State of California's West Nile Virus hotline at 877-WNV-BIRD or at www.westnile.ca.gov.