Fogging Against Dengue
In Kuala Lumpur (and elsewhere in Malaysia), you can often see (and smell) that a building suddenly disappears in fog. This socalled fogging is a measure to fight the Aedis mosquito that transmits the virus. The mosquitos larvae develop in standing water (drains, old cans, pots etc.). Dengue fever is still common in Malaysia, especially in the cities, and many Malaysians catch Dengue Fever sometime in their lives. Hence, the fogging is conducted regularly.