Mosquito pest control. Health worker spraying a house with insecticide to kill mosquitoes. The insecticide is sprayed in a vapour form, so the process is called fumigation. Mosquitos can transmit several diseases to humans, and killing them can reduce infection rates. This fumigation was carried out as part of a weekly inspection during an epidemic of dengue fever. This is caused by several viruses transmitted to humans through mosquito bites. Photographed in Cuba.