West Nile Virus in Kern County

West Nile virus is spread by mosquitoes, mainly Culex mosquitoes that bite in the early morning and evening. There is no vaccine and no medicine for it, per the CDC. What you can control is standing water around your home and whether mosquitoes get a chance to bite you.

The Kern County numbers

These figures come from the California Department of Public Health at westnile.ca.gov:

• 2026 so far: 10 human cases in Kern through October 23, 2026. Kern also had 128 West Nile-positive mosquito samples. Each sample can contain up to 50 mosquitoes. Kern's 2026 rate so far is 1.10 cases per 100,000 people, close to the statewide 1.16.
• In 2025, 21 infections in Kern, a rate of 2.09 per 100,000 people, against 0.30 statewide. That is about seven times the state rate.
• In 2024, 12 infections in Kern, 1.32 per 100,000, against 0.33 statewide, about four times the state rate.

Statewide, 2026 has been a heavy year. As of October 23, CDPH reports 452 human cases in 24 counties, including 29 deaths, plus 4,075 positive mosquito samples and 753 positive dead birds. CDPH calls it the highest West Nile activity in five years.

Reported West Nile virus infections per 100,000 people

Kern CountyCalifornia

The full year-by-year comparison is on our data page.

What West Nile virus does to people

The CDC estimates that about 80% of human West Nile infections cause no symptoms at all. Most of the people who do get sick have West Nile fever, a flu-like illness. Symptoms usually start 2 to 6 days after the bite, though the range is 2 to 14 days.

The serious form is neuroinvasive disease, which affects the brain and nervous system. According to the CDC:

• Fewer than 1% of infected people develop neuroinvasive disease.
• Among those who do, about 10% die. The rate is about 20% for people 70 and older and about 2% for people under 50.
• Older adults are at higher risk, as are people with any of these conditions:
  • cancer
  • diabetes
  • high blood pressure
  • kidney disease
  • a weakened immune system

The CDC says most people with mild illness recover completely. Fatigue and weakness can still last weeks or months. Severe cases usually need hospital care. If someone in your house is older or has one of those conditions, take bite prevention more seriously than you would for a healthy 30-year-old, and have them see a doctor if they come down with a fever during mosquito season.

How the virus moves through a neighborhood

West Nile virus lives mostly in birds. The Kern Mosquito and Vector Control District notes that Culex mosquitoes feed mainly on birds, which is how the virus builds up in a local bird population over the summer. When an infected Culex later bites a person, the person can be infected too.

That is why the same few signals keep showing up in CDPH reports: dead birds, positive mosquito samples, and then human cases. Several dead birds on your street or a run of positive samples in your ZIP code is a reason to tighten up on repellent and standing water right away, before anyone in the house gets sick.

How Kern tracks it

The Kern district runs routine mosquito surveillance: it identifies mosquito species, monitors disease in mosquito populations and targets control work at high-risk areas. It says Kern County has around 26 mosquito species. Statewide, CDPH also tracks dead birds, sentinel chicken flocks and infected horses. As of October 23, 2026 it had counted 753 positive dead birds, 149 positive sentinel chickens and 17 infected horses across California. Each of those numbers is an early warning that the virus is active before people get sick, and CDPH says dead bird reports often show the virus is active in an area before other signs appear.

When the season runs in Kern

In 2026, statewide symptom onset dates ran from June 8 to October 5. That lines up with Bakersfield's heat. At Meadows Field the median first 90-degree day is April 14 and the median last is October 13, with 113 days a year at 90F or hotter on average (our NOAA data). Warm weather speeds up mosquito breeding: UC IPM says that in summer a mosquito can go from egg to adult in a week or less.

Average days per month at 90°F or hotter, Bakersfield Meadows Field

Culex mosquitoes, which UC IPM calls the most important carriers of West Nile virus, are most active in the early morning and evening. That is when to cover up or stay inside. Kern also has the invasive Aedes aegypti, a daytime biter, so you can get bitten in the afternoon too. Our mosquito control page covers the difference.

Repellents that work

The CDC recommends EPA-registered insect repellents with one of these active ingredients:

• DEET
• Picaridin (called icaridin outside the US)
• IR3535
• Oil of lemon eucalyptus (OLE)
• Para-menthane-diol (PMD)
• 2-undecanone

Look for an EPA registration number on the label, and follow the label. For children, the CDC says not to use OLE or PMD on kids under 3, not to put repellent on a child's hands, eyes, mouth, cuts or irritated skin, and to spray it on your own hands first and then apply it to the child's face. Netting over strollers and baby carriers helps with infants.

UC IPM says repellents typically last 4 hours or less. Heat and sweat shorten that, as do wind and humidity. On a Bakersfield summer evening you may need to reapply sooner than you expect. Long sleeves and long pants help too, as do intact window and door screens and running the air conditioning instead of opening windows.

I would skip the gadgets. UC IPM lists ultrasonic emitters and electronic repellers as ineffective and calls bug zappers counterproductive.

Cut the breeding water at home

The CDC's advice is to deal with anything that holds water once a week:

• Empty it and scrub it.
• Turn it over.
• Cover it.
• Throw it out.

Around Bakersfield homes the usual sources are:

• pot saucers
• pet dishes
• bird baths
• kiddie pools
• toys
• leaky irrigation valve boxes
• yard drains
• neglected pools

Scrubbing matters for the invasive Aedes, whose eggs stick to container walls and survive drying out.

If you have done that and are still being bitten, a licensed company can walk the property and find what you missed. We only refer companies licensed by the California Structural Pest Control Board.

Report dead birds

Dead birds are often the first sign that West Nile virus is active in a neighborhood. Report them to CDPH online at westnile.ca.gov or by calling 1-877-WNV-BIRD (1-877-968-2473). CDPH accepts reports year-round. Call center staff will tell you whether the bird can be picked up for testing or how to dispose of it safely. Do not touch a dead animal with bare hands. CDPH notes you cannot catch West Nile virus by touching a dead bird. Gloves or a plastic bag are still the right call.

Report a mosquito problem

Kern County has four public mosquito districts. For Bakersfield, Shafter, Wasco, Lamont, Arvin and Buttonwillow, it is the Kern Mosquito and Vector Control District at (661) 589-2744 or kernmosquito.com. You can report a mosquito problem, report a green swimming pool (anonymously, if you choose), or request mosquitofish for a pond or trough. The district asks you to allow up to 72 business hours for staff to contact you about a mosquito report.

Delano, Taft and the Southfork area have their own districts, and some parts of the county are covered by none. Our mosquito control page lists each district and its phone number. Area pages: Delano, Taft, Lamont, Arvin.