The World Health Organization now recommends spatial emanators indoors alongside insecticide-treated nets. Here is what that guidance covers, what the trials showed, and what remains unproven.
What WHO actually recommended
On 13 August 2025 the World Health Organization recommended spatial emanators for malaria vector control and prequalified the first two products. Spatial emanators, also called spatial repellents, release an active ingredient into the air. WHO states that they kill mosquitoes, deter them from entering treated spaces, and stop them locating and biting people. The recommendation is conditional and applies indoors, in addition to insecticide-treated nets, for preventing and controlling malaria in children and adults in areas with ongoing transmission. WHO also notes one practical advantage. Emanators may add protection against daytime biting, when people are active at home and not sleeping under a net. In short, this is an addition to nets, never a replacement for them.
How the guidance is published and updated
The WHO guidelines for malaria are published in several languages. The recommendation for spatial emanators dates from the 13 August 2025 update (WHO). WHO describes its recommendations as continuously reviewed and updated when the evidence justifies it, and hosts them as a living guideline on the MAGICapp platform. Each updated recommendation displays the date of its most recent revision. This matters to any reader checking a claim. A downloaded copy ages quietly. The platform version carries a date, so the current wording of a recommendation can be verified rather than assumed. Check the platform version directly, because a downloaded copy carries no guarantee that the wording still reflects the current recommendation.
The evidence behind the recommendation
WHO based the recommendation on moderate certainty evidence from five studies that independently evaluated passive emanators and mosquito coils against malaria. The trials assessing passive emanators were conducted in settings where other malaria control tools, such as insecticide-treated nets, were already in use. A first trial in Peru found that emanators reduced arbovirus infection in the study population, and a second trial in South East Asia had recently been completed, with analyses under way. The conditional wording reflects that mixed picture. Moderate certainty is meaningful support, not proof of universal effect. WHO also lists what the evidence does not yet settle, including effectiveness when emanators are used alone, outdoor protection, use in humanitarian emergencies, and insecticide resistance management. Those gaps are stated openly rather than hidden. The conditional status signals that benefits are judged likely to outweigh harms, while the strength of the supporting evidence remains moderate rather than high.
The Kenya trial result
A cluster randomised controlled trial ran in Busia County, western Kenya, an area of high malaria transmission, insecticide resistance and universal coverage of insecticide-treated nets. The trial used 58 clusters and enrolled children aged six months to under ten years. The intervention was a transfluthrin based spatial repellent distributed after a mass net distribution, with a four month baseline and a 24 month intervention period. The primary outcome was first-time malaria infection measured by microscopy. The spatial repellent reduced the hazard rate of first-time infection by 33.4 per cent, with a 95 per cent confidence interval of 11.1 to 50.1. No adverse events or serious adverse events were judged to be linked to the repellent.
The Indonesia trial result
A cluster randomised, double blinded, placebo controlled trial in Sumba districts, Indonesia, used transfluthrin passive emanators that release the active ingredient without an external heat source. Households received two units per nine square metres, replaced every two weeks. Across the full set of 24 clusters, protective efficacy was 27.7 per cent against first-time infections, with a 90 per cent confidence interval of minus 21.3 to 56.9. That result was not statistically significant, and reductions in mosquito landing rates, 16.4 per cent indoors and 11.3 per cent outdoors, were also not significant. In a subgroup of twelve moderate to high risk clusters with entomological data, protective efficacy reached 60 per cent and 66 per cent. The authors concluded that the results suggest spatial repellents prevent malaria, while calling for more evidence.
What this means for a household
Treat an emanator as an extra layer, not a substitute. If you live where malaria transmission continues, keep insecticide-treated nets in use. Nets protect sleeping people. Emanators add airborne protection in rooms where people are awake, which is the daytime gap WHO highlights. Placement, room size and replacement timing follow the product instructions, because emission fades with time. If you are pregnant, caring for a young child, or managing a household in a high transmission area, ask a clinic or local health service what is appropriate for your setting. Public health guidance is written for populations. Your health worker knows your local risk, season and resistance pattern. Ask about local transmission season, circulating species and any known resistance, then follow that advice alongside the product label instructions you already have access to.
Claim honestly, including the gaps
Two well known failure modes appear when a new tool enters public health messaging. One is overclaiming, where a conditional recommendation becomes a guarantee. The other is fear selling, where risk language is sharpened until readers buy something. Neither helps. The honest position is narrower and firmer. WHO supports indoor emanator use alongside nets in areas with ongoing transmission, on moderate certainty evidence. Two peer reviewed trials found reduced infection, one clearly significant and one not significant overall, with a stronger signal in higher risk clusters. Effects on arbovirus infection come from a first trial in Peru. Questions about standalone use, outdoor protection and resistance management remain open. Say all of that, and the guidance still stands on its own.
Sources
- WHO recommends spatial emanators for malaria vector control and prequalifies first two products: World Health Organization
- WHO guidelines for malaria: World Health Organization
- Effect of a spatial repellent on malaria incidence in an area of western Kenya characterised by high malaria transmission, insecticide resistance, and universal coverage of insecticide treated nets (part of the AEGIS Consortium): a cluster-randomised, controlled trial: The Lancet (record held by the Liverpool School of Tropical Medicine)
- Efficacy of a Spatial Repellent for Control of Malaria in Indonesia: A Cluster-Randomized Controlled Trial: American Journal of Tropical Medicine and Hygiene
This article is general information, not medical advice. Ask a doctor or pharmacist about your own health.