Mosquitoes infected with West Nile virus (WNV) were found in Davis a few weeks ago. The Sacramento-Yolo Mosquito and Vector Control District (SAYO) confirmed that they found two mosquito samples infected with the virus and two dead birds, in addition to many more found in the Sacramento County.
SAYO conducts surveillance for mosquitoes infected with WNV and other diseases weekly throughout each year. They have found the virus in both the Yolo and Sacramento counties since its invasion in 2004. However, the activity has been detected earlier than usual this year.
“A [greater than] 5-year period since the previous outbreak has allowed bird immunity to dissipate and corvid [crow, magpie and scrub-jay] populations to rebound. A warm winter, March rains and now warm weather have combined to provide conditions suitable for virus amplification,” said William Reisen, research epidemiologist at the Center for Vectorborne Diseases in Davis, in an e-mail interview. “The SAYO surveillance program tests lots [pools] of mosquitoes and dead birds reported by the public, and have discovered and reported multiple positives early this year.”
The infected mosquito samples were collected near Arroyo Park and Redwood Park in West Davis. Other samples were also found in the Gerber-Bradshaw area of the South Sacramento County.
“This virus activity detected in the mosquito population is about a month early. Typically we don’t detect infected mosquito samples until July,” said District Manager of SAYO David Brown in a press release.
The district is in emergency planning mode to contain the virus and reduce the threat to the public.
“In response to the detection of WNV activity, the district is following the Mosquito and Mosquito Borne Disease Management Plan and will increase its mosquito trapping and surveillance in the area to find sources where mosquitoes may be breeding,” said Public Information Officer of SAYO Luz Rodriguez in a press release. “Ground spraying may also be conducted to rapidly decrease the numbers of infected adult mosquitoes.”
People are encouraged to take precautions against this recent outbreak by using mosquito repellent when outdoors. Personal characteristics such as age, health, immune system, high blood pressure and diabetes can put certain people at a greater risk for contracting the virus.
“There is no vaccine for humans. Horses are vaccinated each year, which provides protection. There are no drugs, so once a case progresses to serious illness only supportive therapy can be administered,” Reisen said. “In humans there is recent evidence that even febrile illness can produce long-term infection and kidney disease. Neurological disease can resolve or provide permanent impairment.”
“The most important thing that people can do to prevent mosquitoes is to not have any dirty water around their yard. Next, personal protection against mosquito bites is best. Always wear an effective mosquito repellent to keep mosquitoes from biting, especially if you are doing any outdoor activities around dawn and dusk when mosquitoes are most active,” Rodriguez said. “We also ask that the public report any dead birds because they provide valuable information as to how the virus is moving.”
Additional information about the recent WNV outbreak can be found at fightthebite.net and residents can also subscribe to mailing lists to stay updated.
PAAYAL ZAVERI can be reached at email@example.com.