It’s the middle of August and the West Nile virus still hasn’t
rampaged through Santa Clara County.
Gilroy – It’s the middle of August and the West Nile virus still hasn’t rampaged through Santa Clara County. Not yet, anyway.
Five months have passed since pest control officials predicted that Santa Clara County would be at the epicenter of an outbreak and not a single horse or human in the county has contracted the disease. Still, those officials said Monday there are ominous signs that their predictions may still prove right.
“Mosquitoes are loaded up with the virus so now the virus is able to be transferred to humans,” said Kriss Costa, a spokeswoman for county vector control. “We could have people right now who have been infected but they haven’t been to the doctor.”
West Nile is a flu-like virus transferred to horses and humans by mosquitoes that have bitten infected birds. Last year, the county found 86 infected birds. So far this year, more than 40 positive birds have been identified and vector control engineers have discovered five positive mosquito pools in south San Jose. Because the virus has a two-week incubation period, Costa said, people in that area may already be infected.
Statewide, 174 people have been infected and four Californians have died. At this time last year, there were 168 cases and five deaths. By the end of mosquito season, 830 people were infected and 28 people died. And predictions that the virus would take hold in northern California this summer have held.
“We talked about northern California being the epicenter and I think the evidence shows that is the case,” said Ted Toppin, of the Mosquito and Vector Control Association of California. “We were correct in our prediction that it would move north but it’s tough to predict where exactly it will take root. Unfortunately, it has set up camp in the Central Valley and taken its toll.”
Sacramento County has been hit the hardest, with 36 human cases. The four deaths have occurred in Fresno, Kings, Riverside and San Joaquin counties. For now, South County seems safe. Even the most peripatetic mosquitoes have a range of just five miles. Only one positive bird has been found in South County, and that was in February.
“Does that mean people in Gilroy don’t need to worry?” Costa said. “No. Everyone needs to worry.”
Costa said that is easier for vector control technicians to combat the disease in South County because they have access to the waterways where mosquitoes are likely to breed. South San Jose is a “hot spot” for the virus because it is heavily populated with people, swimming pools and other dangerous sources of standing water.
“That could be the big factor that plays into this whole thing,” she said. “In Gilroy and more open areas we have access to all the public sites. We’re constantly checking creeks, but we can’t get into people’s backyards.”
San Jose’s mild summer has helped keep down mosquito activity. The pests thrive in hot weather, especially after several consecutive days of temperatures in the 90s. But San Jose was unseasonably cool in June and has posted normal temperatures in the low 80s through July and August, all while Gilroyans have endured weeks of readings near 100.
‘We don’t have near the number of bites we would have if we’d four or five days of hot weather,” Costa said. “And they should start dropping off as weather gets cooler. If we come up with real hot weather in September-October that could change everything. We’re not going to be surprised by anything.”
In the rest of the state, the virus has spread as experts predicted. According to epidemiologists, the virus generally explodes a year after it reaches an area, and then drops off.
Last year, West Nile was epidemic in southern California. In San Bernardino County, 12 of every 1,000 residents were infected. This year, only eight San Bernardino residents have contracted the virus, and there have been just two cases in Los Angeles County. Meanwhile, the virus has flourished in the north, particularly in the Central Valley and Sacramento area.
Officials there have begun spraying the pesticide pyrethrin, a derivative of a chemical found in chrysanthemums. State legislators included about $12 million in the latest budget to fight the virus. Santa Clara County should receive $200,000, which will be used to hire more field technicians.
Case history
California counties with the most human cases of West Nile virus:
Sacramento 36
Riverside 24
Fresno 19
Kings 18
Tulare 17
Kern 15
