ANTIOCH — A wet winter followed by this week’s temperatures in the 80s and 90s may kick-start the West Nile virus season, according to the Contra Costa Mosquito and Vector Control District.
“With all the rain we had this year, there are many more water sources,” spokeswoman Deborah Bass said. “Mosquitoes go through their life cycles faster when the weather is warmer. That means you have more mosquitoes producing more mosquitoes quicker.”
In 2010, the first confirmed case of West Nile virus in Contra Costa did not occur until July 28, with a dead bird. But the weather was milder than is expected this year, Bass said.
“I think there’s the potential for more West Nile activity in 2011 as compared to 2010,” said Vicki Kramer, chief of the Vector-Borne Disease Section at the state Department of Public Health.
This year in Northern California, there have been two confirmed cases of West Nile in birds. One was in Sacramento County and the other in Sunnyvale last week, according to the state health department.
“Historically, East County is where we see the majority of our West Nile activity,” Bass said. “The weather gets much hotter there, and also there’s a lot more birds.”
Mosquitoes pick up the virus when they bite birds and spread it to people when they bite them. Crows, ravens, sparrows and hawks are among the most highly susceptible to the virus. So are squirrels.
The Contra Costa district last week received five flocks of chickens from the state that will be used to provide an early warning that West Nile virus has arrived. The flocks have been positioned in key spots throughout the county, and their blood will be tested every two weeks.
“If the chickens show antibodies for the various diseases we are checking for, we will know there is virus activity in that location,” Bass said. “That means we can concentrate our control efforts in those specific locations.”
In people, the virus most often causes flu symptoms, but in rare instances it can be fatal. The majority — 80 percent — of people bitten by a mosquito carrying the virus will have no symptoms, said Susan Farley, a communicable disease controller for Contra Costa Health Services. About 20 percent will have a fever, headaches, a rash or swollen lymph nodes.
Less than 1 percent have severe reactions that can be fatal, such as brain swelling, loss of consciousness or seizures.
Between 2006 and 2010 in Contra Costa County, four or five cases of West Nile virus in people were confirmed each year. In 2006, two people died from complications of the virus.
“A lot more people get the virus, but since it presents itself with flu-like symptoms, a lot of people don’t go to the doctor,” Bass said.
The vector control district is preparing to fight mosquitoes by setting traps in areas with large mosquito populations, spraying pesticides, dropping mosquito larvae-killing tablets down sewer drains and emptying pools of standing water.
“Our biggest issue still remains neglected swimming pools due to foreclosures,” Bass said. “A neglected swimming pool can produce more than a million mosquitoes and affect people up to five miles away.”
Contact Roman Gokhman at 925-779-7189. Follow him at Twitter.com/RomiTheWriter.
To report a dead bird or squirrel in your area, call 877-968-2473 or go to www.westnile.ca.gov.
Source: Contra Costa Health Services