How to fight West Nile virus in your backyard

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If you’re at home right now, the Sacramento-Yolo Mosquito & Vector Control District wants you to do something really quick: Go outside and flip over that bucket. 

You know the one. It’s sitting in the shade behind the wood pile and it always has a small pool of water in it. Flip it over, and while you’re at it, tip the water out of your neglected bird bath (no judgment!). 

Before you get rid of the liquid, you might notice a row of small black dots along the water’s edge, or some fuzzy green moss rippling near the surface. That’s what we’re trying to avoid, the District says, mosquito eggs and adolescent insects. 

A box of mosquitos at various stages of the lifecycle helps train residents to identify mosquito larvae, Tuesday, Aug. 22, 2023.Andrew Nixon / CapRadio

Mosquitoes are the vectors for a host of undesirable diseases — including West Nile virus — and this season, you may be unwittingly breeding more. 

West Nile is a disease that originates in birds and is passed to humans and other mammals through mosquitoes. Most people (eight out of 10) never develop symptoms, but some do develop a fever and a rash or other flu-like symptoms. In rare instances, people can become very sick with a neuroinvasive case, resulting in diseases like meningitis, encephalitis, and acute flaccid paralysis.

Although cases and deaths occur every year, this summer, West Nile virus in the Sacramento region has been particularly intense, with high numbers of birds and mosquitoes testing positive early in the season. Cases in humans have begun creeping up, too. 

This week, Sacramento and Yolo counties both announced deaths related to the virus. They’ve been added to the state’s count of fatal cases, which currently stands at five. 

Cases increase across the region

As of Wednesday evening, Sacramento County officials said they have confirmed or are investigating at least 16 human cases of WNV. They also announced Wednesday that one person has died from complications related to the virus. The person was in their 70s, had underlying health problems and died in late July after being hospitalized with a neuroinvasive case of the virus.

“This is a reminder that West Nile Virus is a serious disease and unfortunately, can result in death, especially for the elderly and those with compromised immune systems,” said county Public Health Director Dr. Olivia Kasirye in a news release on Wednesday. 

At least three of the Sacramento County cases reportedly resulted in neuroinvasive disease, and about a dozen cases under investigation resulted in a hospitalization.

Yolo County reported their first human death from the virus on Thursday. In an update, they wrote they’ve seen eight human cases already this season, compared to last years’ total of three. Stanislaus County officials also reported four human cases of the virus this week.

Preventing mosquito breeding in the region

Since the beginning of the West Nile season, the Mosquito & Vector Control District has been conducting survey trips to monitor conditions in the field. 

Earlier this week, field technicians David Smith and Ryan Wagner visited the backyard of an Elk Grove bungalow, where they set mosquito traps. Any of the insects caught in their traps are tested for West Nile virus and other dangerous pathogens. 

David Smith with Sacramento-Yolo Mosquito and Vector Control District, checks for mosquito in standing water at an Elk Grove, Calif., home on Tuesday, Aug. 22, 2023.Andrew Nixon / CapRadio

They’re not just tracking the prevalence of viruses in the community; they’re also learning more about the mosquitoes of the region. 

“It's been busy for us,” said Smith. “Part of us going out and doing that surveillance and setting these traps, it also gives us a good indicator of those of the species that can vector West Nile.”

The technicians also assessed the backyard for any stagnant water sources where mosquitoes could breed. Even inches of water in plastic planters had to be tipped out. They say they need residents’ help to eliminate breeding sources on their properties.

David Smith with Sacramento-Yolo Mosquito and Vector Control District, checks for mosquito in standing water at an Elk Grove, Calif., home on Tuesday, Aug. 22, 2023.Andrew Nixon / CapRadio

“Within our district boundaries, we have just over 465,000 [land] parcels,” said Smith. “So covering that ground with our crew specifically — we have five technicians. It's a tall task.”

The West Nile virus intensity this summer has already prompted the agency to do urban aerial spraying for the first time since 2018. In early August, they sprayed areas over Woodland and Davis with a diluted insecticide, called Dibrom, from a low-flying plane. They’ve also been regularly spraying backyards and agricultural areas. 

Since there is currently no vaccine or specific treatment for WNV, the agency is asking the public to do what they can to prevent being bitten — including wearing a strong repellent and loose-fitting long clothing, especially near dawn and dusk. 

Those who are interested can monitor the spread of the disease in California on westnile.ca.gov and can learn about any future planned spraying operations near them on fightthebite.net.