The Centers for Disease Control and Prevention said Wednesday that it had confirmed at least 48 cases of West Nile virus with 38 of them severe as of June 30, marking the earliest and worst start to the season in over two decades. Since 2004, the average number of cases reported by the end of June has been around 10, making this year’s surge exceptionally alarming to public health officials.
Federal health officials said 23 states have reported finding West Nile virus, the most in a decade. The virus has spread across the country with particular intensity in Arizona, where most cases have been concentrated. Of the state’s 32 total cases, 29 are in Maricopa County, which includes Phoenix. The county has recorded four deaths from the virus so far in 2026, a tragic toll that underscores the severity of the outbreak.
“These findings serve as an important reminder that mosquito season is well underway,” said Dr. Erin Staples, a CDC expert on insect-borne diseases. “As families gather outdoors to celebrate Independence Day, we encourage everyone to enjoy their holiday while taking simple steps to protect themselves and their loved ones from mosquito bites.”
The CDC recommends several prevention strategies to reduce the risk of infection. People should use EPA-registered insect repellent, including products containing DEET, picaridin, IR3535, or oil of lemon eucalyptus. Wearing long, loose-fitting clothes when outside makes it harder for mosquitoes to bite exposed skin. Experts also suggest avoiding being outdoors around dusk and dawn, when the mosquitoes that carry the virus are most active.
Residents should also eliminate breeding grounds for mosquitoes. Officials in Maricopa County emphasized that even small amounts of standing water can support mosquito reproduction. “Even an overturned bottle cap can hold enough water for mosquitoes to breed,” said Melissa Kretschmer, a county health department official. Homeowners should patch up broken window screens, install or repair door and window screens, and get rid of any standing water around their properties.
Most people infected with West Nile virus experience no symptoms or only mild ones such as headaches, body aches, joint pain, vomiting, diarrhea and rashes. However, scientists say many people—perhaps tens of thousands each year—are infected without knowing it. In severe cases, damage to the central nervous system causes potentially deadly inflammation of the brain or spinal cord. Adults older than 60 and people with underlying medical conditions or weakened immune systems face the highest risk of such complications.
West Nile virus was first reported in the United States in 1999 in New York, and then gradually spread across the country. It peaked in 2003, when nearly 10,000 cases were reported. Since then, the disease has remained a persistent public health concern. In the last decade, health officials have fielded reports of approximately 2,000 cases annually on average, including about 1,200 life-threatening neurological illnesses and roughly 100 deaths.
The virus is spread to people through the bites of infected mosquitoes. There is no licensed vaccine or approved treatment available to prevent West Nile virus infection in people. The only effective approach is prevention through mosquito bite avoidance and mosquito control efforts at the community and household level.
Health officials are particularly concerned about the early timing of this year’s outbreak and its potential to worsen as summer progresses. Positive mosquito pools have been confirmed earlier than usual in several regions including San Antonio, Frisco, New Orleans, and six California counties. The early season start suggests potential for above-average transmission during peak summer months, when mosquito populations typically reach their highest levels.
As the summer season advances, public health agencies across the country are ramping up surveillance and mosquito control efforts. Communities are being urged to remain vigilant about the disease and take personal precautions seriously. The confluence of an unusually early start, high case numbers, and widespread geographic distribution of the virus has prompted the CDC to issue its urgent warning to the American public as Independence Day approaches and outdoor gatherings increase.