Community wide transmission of malaria and considering a buffer zone.
Although most mosquito vectors of malaria have a flight range of around 2km, this can vary considerably (for instance, one of the major Pacific vectors has an average flight range of about half this) and flight ranges greater than about 5km are not usual. Mosquitoes can spread malaria within their flight ranges so a new works site for example located within a few kilometres of an endemic community can quickly become a focus of transmission.
In areas of high transmission older children and adults develop a high degree of immunity to the disease and harbour parasites without developing symptoms. These individuals act as a permanent reservoir of parasites for the local mosquito vectors to pick up and pass on.
When considering site-wide vector control approaches, it is often wise to consider expanding control efforts into the surrounding communities to create a buffer zone of lowered transmission around the site. Where IRS is used this is particularly important since this control approach relies on achieving a community-wide impact on the mosquito vector population, shortening the average mosquito life span so that individual mosquitoes don’t live long enough for the parasite to have sufficient time to develop in the mosquito and be passed on.