West Nile virus at 5-year high in California: Protecting children

With West Nile virus (WNV) activity in California reaching its highest level in 5 years, pediatric clinicians may be fielding more questions from families about mosquito bites and how to prevent them. Children's Hospital Los Angeles (CHLA) has issued caregiver-focused guidance centered on bite prevention as the primary defense.¹

Michael Smit, MD, MSPH, hospital epidemiologist and medical director of infection prevention and control at CHLA, urged families to follow state and county public health recommendations, which he said include "using EPA-registered insect repellents, wearing long sleeves and pants, and draining standing water."¹

West Nile virus surge in California and Southern California hotspots

The California Department of Public Health (CDPH) declared WNV activity at a 5-year high in August, reporting 30 human cases, including 3 deaths, across 13 counties as of August 14—above the 5-year average for that point in the season.² According to CHLA, the highest concentrations of infection have been reported in Southern California, including East Los Angeles, the San Fernando Valley, and South Bay communities such as Long Beach and Cerritos.¹

CHLA attributed increased mosquito activity to unseasonably warm, rainy, and humid weather, including El Niño patterns, noting that warmer winters let mosquitoes thrive year-round.¹

West Nile fever and neuroinvasive disease in children

Most children infected with WNV never develop symptoms, and the CDC estimates that about 80% of human infections are subclinical or asymptomatic.¹,³ CHLA estimates that roughly 20% of infected children develop West Nile fever, which can present with fever, headache, myalgia and arthralgia, nausea or vomiting, and rash.¹

In fewer than 1% of infections, the virus involves the central nervous system, causing encephalitis, meningitis, or acute flaccid myelitis.¹ CHLA considers this a medical emergency; warning signs include high fever, neck stiffness, disorientation, muscle weakness, and tremors.¹ Neuroinvasive risk rises with age but is not limited to older adults, and overall fatality is approximately 10%, with long-term neurologic sequelae common among survivors.³

Insect repellent guidance for infants and children by age

CHLA recommends repellents registered with the Environmental Protection Agency (EPA).¹ For children aged 2 months and older, common active ingredients include DEET (20%-30%), picaridin (10%-20%), and 2-undecanone (7.5%); oil of lemon eucalyptus (para-menthane-3,8-diol [PMD]) and IR3535 are listed for children aged 3 years and older.¹ The American Academy of Pediatrics (AAP) likewise advises against oil of lemon eucalyptus or PMD in children younger than 3 years.⁴

Concentration governs duration of protection. CHLA notes that lower-concentration formulas are generally recommended for children, such as 10% DEET, which protects for up to 2 hours.¹ AAP guidance indicates 30% DEET lasts about 5 hours, concentrations above 50% add no further duration, and 20% picaridin may protect for 8 to 12 hours.⁴ The AAP advises choosing the lowest concentration that covers the expected time outdoors, applying DEET sparingly in children younger than 2 years, and using particular caution in newborns and premature infants.⁴

Permethrin, protective clothing, and mosquito habitat reduction

CHLA recommends insect netting over strollers, car seats, and playpens; loose-fitting long sleeves and pants, layered when possible; and intact window screens.¹ Outer clothing can be treated with 0.5% permethrin spray, which CHLA notes can last through multiple washes; the AAP specifies that permethrin belongs on clothing and gear, not skin.¹,⁴ Families can also reduce breeding sites by regularly emptying standing water from buckets, open trash cans, kiddie pools, and flowerpots, and by limiting prolonged outdoor time around dawn and dusk.¹

References

1. Children's Hospital Los Angeles. Kids, mosquito bites, and West Nile virus: guide for caregivers. Newswise. October 28, 2026. Accessed October 29, 2026. https://www.newswise.com/articles/kids-mosquito-bites-and-west-nile-virus-guide-for-caregivers

2. California Department of Public Health. West Nile virus activity at five-year high. News release NR26-026. August 20, 2026. Accessed October 29, 2026. https://www.cdph.ca.gov/Programs/OPA/Pages/NR26-026.aspx

3. Centers for Disease Control and Prevention. Clinical signs and symptoms of West Nile virus disease. Accessed October 29, 2026. https://www.cdc.gov/west-nile-virus/hcp/clinical-signs/index.html

4. Balk SJ. How to choose an insect repellent for your child. HealthyChildren.org. American Academy of Pediatrics. Updated June 21, 2024. Accessed October 29, 2026. https://www.healthychildren.org/English/safety-prevention/at-play/Pages/Insect-Repellents.aspx