Overview
- As of late March, very high activity is affecting foothill cities from Altadena to Sierra Madre, with adults able to travel up to five miles from rivers.
- Traps that caught only single digits last year now hold hundreds, with some counts above 500.
- Officials link the spike to an early heat wave and snowmelt that raised river flows, which create ideal breeding in fast‑moving water.
- Vector control crews are treating river sites weekly and started earlier than usual, yet they expect adult flies already out to persist for several weeks.
- The district says bites are painful but not linked to disease in L.A. County and urges DEET repellent of at least 15 percent, full‑coverage clothing, face netting, and turning off fountains for 24 hours.