) ▁and ▁prompt ▁treatment ▁of ▁confirmed ▁cases ▁with ▁ar tem is in in - based ▁combination ▁ther ap ies ▁( ACT s ). ▁While ▁previously ▁the ▁W HO ▁had ▁recommended ▁I RS ▁only ▁in ▁areas ▁of ▁sp or adic ▁mal aria ▁transmission , ▁in ▁ 2 0 0 6 ▁it ▁began ▁recomm ending ▁I RS ▁in ▁areas ▁of ▁en demic , ▁stable ▁transmission ▁as ▁well . ▁ ▁According ▁to ▁the ▁W HO : ▁ ▁Furthermore , ▁for ▁I RS ▁to ▁be ▁effective : ▁▁ ▁There ▁must ▁be ▁a ▁high ▁percentage ▁of ▁sp ray able ▁surfaces ▁within ▁each ▁dwell ing . ▁ ▁The ▁vector ▁( mos qu itos ) ▁must ▁feed ▁or ▁rest ▁ind o ors . ▁ ▁The ▁target ed ▁vectors ▁must ▁be ▁sus cept ible ▁( i . e . ▁not ▁resist ant ) ▁to ▁the ▁insect ic ide ▁being ▁sp rayed . ▁ ▁The ▁W HO ▁further ▁states ▁that ▁" in sect ic ide ▁sus cept ibility ▁and ▁vector ▁behaviour ; ▁safety ▁for ▁humans ▁and ▁the ▁environment ; ▁and ▁effic acy ▁and ▁cost - effect iveness " ▁are ▁factors ▁that ▁must ▁be ▁considered ▁when ▁selecting ▁an ▁insect ic ide ▁for ▁I RS . ▁ ▁Appro ved ▁insect ic ides ▁Currently , ▁the ▁W HO ▁has ▁approved ▁twelve ▁different ▁insect ic ides ▁for ▁I RS . ▁ ▁Cost ▁effect iveness ▁and ▁effic acy ▁According ▁to ▁ 2 0 1 0 ▁C och rane ▁review , ▁I RS ▁is ▁an ▁effective ▁strategy ▁for ▁reducing ▁mal aria ▁inc idence . ▁It ▁is ▁about ▁as