Buzz Off: OC’s Battle Against the World’s Deadliest Pest
Close up of an Aedes aegypti mosquito enjoying an afternoon cocktail.
Photo credit National Institute of Allergy and Infectious Diseases
Californians worry about big things, like earthquakes, wildfires, and droughts. But one of the most persistent threats is hiding in plain sight, thriving in our own backyards. We are in a massive fight with mosquitoes.
The World’s Deadliest Animal
Ask someone what the most dangerous animal is, and they might say sharks, lions, or venomous snakes. But mosquitoes have killed far more humans than those predators combined. These tiny insects are effective carriers of diseases like chikungunya, dengue, and Zika. Here in Orange County, and across California, they’re spreading West Nile virus.
The Big Picture
West Nile virus is spread through a single mosquito bite. Most people who contract it have no symptoms. About 20% experience flu-like illness. Rare but severe neurological complications afflict approximately one out of 150 people with West Nile virus. Unfortunately, West Nile virus is here to stay as part of California’s public health landscape.
In 2025, 36 Californians have contracted West Nile virus and two people died from their infections. Each of those infections began with a tiny mosquito bite. It could have been from one of the 2,260 positive mosquito samples officials have collected so far this year across 27 different counties. Or it could have been from any of untested areas in a neighborhood backyard, park, or school.
Mosquito Hunters
Where are the danger zones? Hyperlocal data in the form of weekly trapping reports from each city show hot spots for mosquito activity. This tells officials where to find and wipe out active breeding grounds before outbreaks occur.
Although mosquitoes are active in Irvine, they are more common in north and central Orange County, as seen in Orange County Mosquito and Vector Control’s most recent data.
Orange County Mosquito and Vector Control’s most recent data (Disease Week 35: August 25th to September 1st) shows that Irvine has the sixth highest population of mosquitos in the county.*
*Data from Aliso Viejo, Los Alamitos, Rancho Santa Margarita, and Trabuco Canyon was not provided.
But just knowing where mosquitoes are is only half the middle. To really make a difference, understand what attracts them in the first place. UC Irvine researchers have found that not all mosquitoes are the same when it comes to preferred habitats. The Aedes aegypti species prefers small containers like the saucer under a flower pot. The Culex species, on the other hand, prefers bigger bodies of water like storm drains, ditches, and freshwater marshes.
A countywide map of mosquito populations shows that the red areas are predominantly inhabited by the species most effective at spreading West Nile virus, the Culex species. These areas are at greater risk of West Nile virus transmission as a result. The green area of the map is dominated by the Aedes species.
Photo credit Orange County Mosquito and Vector Control
Irvine’s Approach
In 2016, Irvine adopted an Integrated Pest Management Program that reduced reliance on powerful pesticides. Instead, the city takes a layered approach to various vectors of disease like mice and rats in addition to mosquitoes.
Prevention first: City designers use strategies discourage pests from settling in the first place.
Non-chemical controls: Techniques like releasing beneficial insects are used before pesticides.
Organic pesticides: These are applied if prevention and non-chemical controls fall short.
Synthetic pesticides: If all else fails, and the threat is understood to be considerable, the city will use synthetic pesticides.
You Play a Role
Positive West Nile Virus Cases by City (Aug 25-Sept 1)
Fighting mosquitoes isn’t just up to the city. The small steps we take can make a big difference:
Dump and Drain: Empty standing water weekly from pet dishes, flowerpots, toys, and even watering cans. To a mosquito, a teaspoon of water is a five-star resort.
Report Dead Birds: They are early warning signs of West Nile virus. Notify Orange County Mosquito and Vector Control to help them catch outbreaks.
Use Repellent: Especially at dawn and dusk, when mosquitoes are most active.
At the end of the day, the state and cities may be on the front lines, but the real battle is fought in our own yards, patios, and balconies. Protecting Irvine from West Nile virus, and keeping annoying mosquitoes at bay, starts at home.