WHO recommends spatial emanators for malaria vector control and prequalifies first two products

The World Health Organization (WHO) has issued a new recommendation supporting the use of spatial emanators, introducing a new class of intervention for malaria vector control.

Spatial emanators – also known as spatial repellents – emit active ingredients into the air to kill mosquitoes, deter them from entering treated spaces, and prevent them from locating and biting human hosts. They offer a promising complement to existing prevention measures such as insecticide-treated nets (ITNs) and indoor residual spraying.  Unlike ITNs, spatial emanators may provide an added layer of protection against day-time mosquito biting, when residents of a household are active within the home and not sleeping under a net.

“This recommendation opens the door to a new intervention for national malaria control programmes at a time when innovation is urgently needed,” said Dr Daniel Ngamije, Director a.i., Malaria and Neglected Tropical Diseases, WHO.  “As rising insecticide resistance and changes in mosquito behaviour threaten the effectiveness of long-standing vector control tools, spatial emanators offer an innovative approach to help protect people at risk from infection.”

“The WHO conditional recommendation for spatial repellents is a significant step forward in providing access to a new malaria vector control intervention,” said Dr Philippe Duneton, Executive Director of Unitaid. “Unitaid is proud to have supported research proving that spatial repellents, when used alongside insecticide-treated nets, can significantly reduce malaria transmission. At a time when progress against malaria has stalled, spatial repellents are the first new class of vector control intervention in decades, offering a new approach to protect people at risk. Unitaid will continue to support efforts to ensure market access for these tools, generate further evidence on their potential as a standalone intervention, and help define a set of use cases.”

WHO has also prequalified two spatial emanators products, Mosquito Shield and Guardian, manufactured by SC Johnson & Son, Inc. The products emit the active ingredient transfluthrin which has the effect of repelling, disorienting and killing mosquitoes which transmit malaria. The products have been shown to remain effective for up to 1-month and 12-months, respectively, meaning that they can be deployed in a variety of settings where replacement strategies and distribution schedules may differ.

The prequalification decision is expected to support procurement decisions at international, regional, and national levels by UN and partner procurement agencies, as well as member states, ultimately enabling faster and broader access to these products in communities with urgent needs.

WHO prequalification programme assesses the quality, safety and efficacy of each submitted product. The complete WHO public assessment reports can be found on the product pages for each product in the list of prequalified vector control products.

This achievement showcases the close and continuing partnership between two departments at WHO headquarters – Malaria and Neglected Tropical Diseases, Regulation and Prequalification – to speed up access to high-impact tools to the people who need them most.

More on the WHO recommendation

WHO has issued a conditional recommendation in support of the use of spatial emanators indoors in addition to ITNs to prevent and control malaria in both children and adults in areas with ongoing malaria transmission. The recommendation is based on moderate-certainty evidence from 5 studies that independently evaluated both passive emanators and mosquito coils against malaria. The trials assessing passive emanators were conducted in settings where other malaria control tools – such as ITNs – were already in use. For more on the recommendation, visit the WHO guidelines for malaria.

While this recommendation marks a major step forward, key evidence gaps remain – particularly around the effectiveness of spatial emanators when used alone, their potential to protect people outdoors or in humanitarian emergencies, and their role in managing insecticide resistance. Global research and funding partners are now working to close these gaps and strengthen the evidence base for spatial emanators.

Beyond malaria, spatial emanators are also being evaluated for their potential to reduce the transmission of dengue virus and other arboviruses. Results from a first trial in Peru found that spatial emanators reduced arbovirus infection in the study population; a second trial in South-East Asia has just been completed and analyses are under way.

Collectively, data from these trials spanning malaria to arboviral diseases will inform future deliberations of the relevant WHO guideline development groups, potentially leading to new and/or updated recommendations for the expanded use of spatial emanators.