West Nile virus detected in southern US mosquitoes weeks early, San Antonio in May and 17 positive samples across six California counties
West Nile mosquitoes are testing positive across the southern US weeks ahead of season. San Antonio recorded its first positive pool in May, with detections in Frisco, New Orleans, and six California counties. No human cases yet, but peak transmission runs July to September.
Residents across the southern United States are seeing West Nile virus appear in local mosquito populations weeks earlier than usual, a pattern public health officials are watching closely heading into summer. San Antonio recorded its first positive mosquito pool in May, an unusually early start. Within the first days of June, positive samples followed in Frisco, Texas and in New Orleans, while California confirmed 17 positive mosquito samples spread across six counties. So far, no human infections have been reported in these areas. West Nile spreads to people through the bite of an infected mosquito, and most people who are infected never develop symptoms. A small share can develop serious neurological illness, which is why early detection in mosquitoes matters: it tends to precede the human cases that peak between July and September. Local governments have moved quickly. New Orleans authorized helicopter-based aerial spraying over parts of the city and surrounding parishes. Frisco expanded larvicide treatments into additional neighborhoods and stepped up environmental surveillance. California continues to track positive samples county by county. The practical advice for anyone in affected regions is the same that holds every summer, now relevant earlier than expected: drain standing water around the home, use repellent, and limit exposure at dawn and dusk when these mosquitoes are most active. An early start does not guarantee a severe season, but it gives the virus more time to circulate before the traditional peak.