CDC Warns of Unusually Early and Strong West Nile Virus Season in 2026

The CDC warns that the 2026 West Nile virus season is off to its earliest and most severe start in over 20 years. By June 30, 2026, health officials confirmed 48 human cases across 23 states, with 38 involving severe neurological complications. Arizona is the current hotspot with 32 cases, primarily in Maricopa County where four deaths occurred. Because there is no vaccine or cure, officials urge the public to use EPA-registered insect repellents and eliminate standing water to prevent bites.

West Nile virus detection

• ▪Arizona recorded 32 of the nation's 48 West Nile virus cases as of June 30, 2026, with 29 cases and four deaths occurring in Maricopa County
• ▪The Long Beach Department of Health and Human Services reported its first human case of West Nile virus in 2026, involving a hospitalized patient who is recovering at home
• ▪The San Gabriel Valley Mosquito and Vector Control District detected West Nile virus in a mosquito collected from Alhambra, California, on June 29, 2026
• ▪As of June 30, 2026, 23 states had reported finding West Nile virus, representing the highest number of states reporting detections in 10 years
• ▪The average number of West Nile virus cases reported to the Centers for Disease Control and Prevention by the end of June is around 10
• ▪The Centers for Disease Control and Prevention confirmed at least 48 human cases of West Nile virus as of June 30, 2026, marking the highest number of early-season cases since 2004

Mosquito transmission patterns

• ▪West Nile virus was first identified in Uganda in 1937, arrived in the United States in New York in 1999, and reached Los Angeles in late 2003
• ▪The risk of West Nile virus transmission increases during hot weather, typically spanning from June to October
• ▪The southern house mosquito, Culex quinquefasciatus, is the primary vector that transmits West Nile virus in Southern California

High-risk populations

• ▪Anyone bitten by an infected mosquito is at risk of contracting West Nile virus, though there is no human vaccine or specific cure available
• ▪People over the age of 50, or those over 60 with underlying medical conditions or weakened immune systems, face the highest risk of severe West Nile virus illness

Infection symptoms

• ▪Approximately 80 percent of people infected with West Nile virus develop no symptoms and remain unaware of their infection
• ▪About 20 percent of infected individuals experience mild symptoms starting 3 to 14 days post-bite, including fever, headache, body aches, nausea, vomiting, and skin rash

Severe neurological complications

• ▪Less than 1 percent of West Nile virus infections lead to severe neurological conditions, such as encephalitis or meningitis, which can cause permanent damage or death
• ▪Of the 48 confirmed West Nile virus cases reported by June 30, 2026, at least 38 involved severe neuroinvasive illness affecting the brain or nervous system
• ▪Over the last decade, the United States has averaged 2,000 West Nile virus cases annually, including 1,200 neurological cases and 100 deaths
• ▪Approximately 10 percent of individuals who develop severe neuroinvasive West Nile virus disease die from the infection

Mosquito bite prevention

• ▪To reduce mosquito breeding, residents are urged to eliminate standing water from containers around their homes, repair window screens, and wear long-sleeved clothing
• ▪Health officials advise using insect repellents containing DEET, IR3535, oil of lemon eucalyptus, or picaridin to prevent mosquito bites