West Nile virus activity is surging in Sacramento County, with the region now leading the state, officials say.
There is also greater and more localized activity this year compared to last year, said Luz Robles, public information officer for the Sacramento-Yolo Mosquito and Vector Control District.
“Residents need to be vigilant, especially as we enter the hottest of the hottest weeks of the year,” Robles said, explaining that heat advances the life cycles of mosquitoes.
West Nile virus activity is defined by the number of dead birds and mosquito samples testing positive for the virus, Robles said. Sentinel chickens and horses testing positive would also be taken into consideration, but there have not been cases of either in California so far this year.
In the majority of cases, the disease is contracted from the bite of an infected mosquito. Mosquitoes become carriers of the disease after feeding on infected birds, such as crows, ravens and finches, which act as hosts for the disease.
More mosquitoes flying around means a greater chance of getting bitten and a greater chance of contracting the virus.
Nine human cases in California have tested positive for the virus. Fresno and San Bernardino counties have reported one positive human case each, and Kern, Los Angeles and Riverside Counties have each reported two positive human cases.
The California West Nile virus website does show one human case in Sacramento County testing positive for the virus, but an official from Sacramento County clarified that the county believes this individual was infected with the virus in 2017 and only just tested this year.
Last week, 15 dead birds tested positive for West Nile virus — 14 of those birds were from Sacramento County. Most local activity is widespread, Robles said, but activity has been specifically identified in Land Park and Elk Grove.
A total number of 50 dead birds from 12 California counties have tested positive for the virus this year, with just over half of those birds collected from Sacramento County.
“Dead bird reports are very important because they are usually the first indication that the virus is active in an area,” the westnile.ca.gov website states.
Locally, on July 11, 31 mosquito samples tested positive for the virus, reports the Mosquito and Vector Control District. These samples, which test from one to 50 mosquitoes at a time, were collected from Elk Grove and Sacramento parks and neighborhoods.
Recently, activity of the virus was identified in Yolo County, with a mosquito sample from Davis testing positive.
After receiving lab results from the Elk Grove mosquito samples showing positive results, the Mosquito and Vector Control District responded quickly, spraying parts of Elk Grove with a treatment aimed to reduce mosquito populations.
Residents can sign up to receive notifications about spraying activity within their ZIP code on the Mosquito and Vector Control District’s website.
The district asks people who see a bird dead for less than 24 hours to report it online on the westnile.ca.gov website or by calling 877-968-2473.
Although most people infected with the disease don’t show symptoms, about 1 in 5 people infected will develop a condition referred to as West Nile fever, with symptoms including headache, body aches, joint pains and fatigue, according to the Centers for Disease Control and Prevention.
The most severe cases — about 1 in every 150 cases — can be life-threatening.
Robles said people should avoid mosquito bites by using repellant, staying inside from dusk to dawn as much as possible or wearing long sleeves and pants when outdoors during these times, and draining all standing water, which acts as a breeding ground for mosquitoes.