The mosquito that carries dengue does not breed in drains or marshland. It breeds in clean, still water within a short flight of a house, and it needs remarkably little of it, a bottle cap will do. That is inconvenient, because it means the breeding sites are almost always on the property rather than somewhere else, and encouraging, because it means a careful walk-round genuinely works.
The walk-round
- Plant pot saucers. The single most common site. Empty them, or fill them with sand so the plant still drinks but nothing can lay in standing water.
- The gutter. Blocked sections hold water for weeks after rain and are impossible to see from the ground.
- Water tanks and storage barrels. Any lid that does not seal, or any inspection gap without a mesh.
- Discarded tyres, buckets, paint tins and building rubble at the side of the house.
- The tray under the fridge, and the drip tray under a wall air conditioner.
- Bromeliads, ornamental bamboo and any plant that holds water where the leaf meets the stem.
- Roof valleys, flat concrete slabs and any ledge that has never quite drained.
- The pet water bowl and the bird bath, if they are not emptied daily.
Why fogging alone is not the answer
Fogging kills adult mosquitoes that are flying at the moment it is done. It has almost no effect on larvae, and none at all on eggs, which in this species can survive months of dryness and hatch when water returns. Fogging during an outbreak is worth doing because it interrupts transmission quickly, but a property that is fogged and not cleared will be back to where it started within a fortnight.
If you share a boundary
Aedes aegypti typically stays within a hundred metres or so of where it emerged, which means an untended plot next door is your problem too. A neighbourhood that clears together gets a result that no single household can achieve alone, this is the reason council drives are organised street by street rather than house by house.