Source – WHO

The mosquito fogging being conducted by the Vector Borne Disease Control Program (VBDCP) will not harm humans, reminds the World Health Organization (WHO) and Solomon Islands Ministry of Health and Medical Services (MHMS).

VBDCP staff from Honiara City Council (HCC) and Guadalcanal Province (GP) have been conducting ‘mosquito fogging’ operations in Honiara and in some areas of GP over the last month. These operations have been in response to the increased numbers of dengue cases that have been recorded, mainly in HCC. Precautionary fogging is also being applied at the major evacuation centres following the flash flooding in early April.

Vector Borne Disease Control Program staff of Guadalcanal Province conducting mosquito fogging operations in a flood-affected community. Photo: WHO/Joy RC

The aim of the mosquito fogging operations is to kill, or ‘knock-down’, any adult dengue mosquitoes that may be carrying the dengue virus. The mosquitoes become infected with the virus after biting and taking blood from someone who is sick with dengue. To try and prevent the infected mosquito from biting another person and passing on the disease, the VBDCP is applying the mosquito fog in areas where a lot of dengue cases have been reported to try to kill as many adult dengue mosquitoes as possible.

The insecticide used in the mosquito fogging is a synthetic pyrethroid that is very similar to the insecticides used in most domestic insect spray cans that are found on supermarket shelves. The ‘fog’ is created by blasting the mixture of insecticide and water into very fine droplets through the fogging machine. The amount of insecticide in the fog is very small, and is dispersed at quantities that can only kill something as small as a mosquito, so at the concentrations used there will be no adverse health effects on people who are occasionally exposed to the fog. The type of insecticide being used in the fogger is also completely odourless.

The ‘mosquito fogger’ is a very large and noisy machine that is transported in the back of a truck. The vehicle has a warning light and is driven slowly around the streets where high dengue numbers have been recorded, blowing the fog into the yards for a distance of up to 90 metres away. It is useful for residents to leave all doors and windows in their house open at the time of fogging, as this will allow the fog to enter the house and kill any mosquitoes inside. Mosquito fogging operations are usually carried out between 5.30-7.30am, or 4.30-6.30pm, as this is the time when the outdoor dengue vector is most active and is looking to bite.

While the fogging operations will have some success in killing adult mosquitoes in the areas that are treated, the residents of Honiara and GP are warned that this activity alone is not enough to protect everyone or prevent all dengue infections. To reduce and control dengue outbreaks a number of actions need to be taken not only by public authorities but also by residents. These include making sure there are no dengue mosquitoes breeding in your yard, such as in tyres, drums, buckets and any water storage containers, and that you also protect your family from mosquito bites inside and outside the house during the day and in the early morning and early evening. The best methods of personal protection are to apply insect repellent and/or to wear long sleeves and long pants.

The MHMS plans to continue with the mosquito fogging operations until dengue case numbers have dropped substantially. The National VBDCP will be publishing a fogging schedule in the newspapers each week, which will list which suburbs they are planning to fog each day. The public are advised by MHMS not to be alarmed when mosquito fogging is being carried out in your area, but to cooperate by staying clear of the moving vehicle and of the fogging machine.


  • Mosquito fogging operations are being conducted at locations in HCC and GP where dengue case numbers are increasing.
  • The insecticide in the fog is not harmful to human at the low concentrations used and it has no odour.
  • Fogging operations are conducted in the early morning or late afternoon.
  • Residents are advised not to be concerned about the fog, and are also requested to leave their doors and windows open when the fogging machine is in their area, so that the fog can kill mosquitoes inside the house.
  • Residents are also advised that they need to continue to prevent dengue mosquitoes breeding in their yard and to protect themselves and their family from mosquitoes bites during the day and in the early morning and early evening.