In the three weeks since San Joaquin County first reported mosquitoes testing positive for West Nile virus, one area has emerged as a hotbed for the infected pests.
More than 80% of the mosquito samples that have tested positive for West Nile virus this summer in San Joaquin County have been found in the Tracy area, officials said.
According to the county’s Mosquito and Vector Control District’s laboratory surveillance and disease testing system, officials have found infected mosquitoes for the last four consecutive weeks in and around Tracy.
Last week, two positive mosquito samples were found in ZIP codes 95376 and 95377, county officials said in a July 10 announcement.
The uptick comes comes less than a month after reports of West Nile-infected mosquitoes were confirmed for the first time this year in San Joaquin County. Officials said that although the positive test results were the first of the season, they are typical for the start of summer. Infected mosquitoes were found about the same time last year.
Since then, 11 of 13 positive mosquito samples in the county have been found in the Tracy ZIP codes, vector control officials said.
Statewide, 19 of California’s 58 counties have reported cases of West Nile virus in mosquitoes, with a total of 539 positive samples. This time last year, the state had reported 320 positive samples.
In addition, two dead birds in San Joaquin County have tested positive for the virus, including a American crow found dead in Tracy the week of June 29. The birds are among 42 shown to be infected across the state.
“Detections of (West Nile virus) in both birds and mosquitoes indicate there is active transmission occurring in the area,” Sumiko De La Vega, the Mosquito and Vector Control District’s assistant entomologist, said in a statement.
West Nile virus is the leading cause of mosquito-borne disease in the continental U.S., according to the Centers for Disease Control and Prevention. It is most commonly spread to people through the bite of an infected mosquito.
Symptoms include fever, headache, body aches, vomiting, diarrhea or rash. According to the CDC, there are no vaccines to prevent or medicines to treat West Nile virus. Last year, a 57-year-old Stockton man contracted the virus in September and received medical treatment at a Sacramento area healthcare facility.
This year, there have been two cases in California of humans infected with West Nile virus, including one in Stanislaus County. A second case, reported earlier in Tulare County, resulted in the death of an adult male.
Reduce your risk
To reduce your risk of contracting West Nile virus, you should take steps to prevent mosquito bites, officials say.
Aaron Devencenzi, the public information officer for San Joaquin County’s Mosquito and Vector Control District, advised residents to remove all standing water that can attract mosquitoes to their property, and to use tight-fitting screens on doors and windows at your home.
Officials said they will be sending second-notice letters to homeowners suspected of neglecting their swimming pools, which can serve as a primary breeding ground for mosquitoes.
People also should take care to:
- Avoid spending time outside when mosquitoes are most active, at dawn and dusk, especially for the first two hours after sunset.
- Wear long pants, long-sleeved shirts and other protective clothing when outdoors.
- Contact your veterinarian for information on vaccinating equines against West Nile virus.
In addition, Devencenzi advised using mosquito repellents registered by the Environmental Protection Agency. Such insect repellents prevent mosquitoes from biting and contain EPA-registered active ingredients including DEET, Picaridin, the repellent form of oil of lemon eucalyptus and IR3535.
To learn more about the county’s Mosquito and Vector Control activities, go to www.sjmosquito.org or call (209) 982-4675 7 a.m.-3:30 p.m. Monday-Friday. Residents can receive spray notifications at www.sjmosquito.org.
The district said it will continue to provide surveillance of mosquito populations and test for mosquito-borne diseases. Nineteen state-certified technicians check 150 to 300 known mosquito sources once a week and respond to service requests from the public. In addition, more than 80 surveillance traps are placed weekly to biweekly to assess mosquito populations and test samples for mosquito-borne diseases, officials said.