Remarks The conditionality of this recommendation is largely driven by the very low certainty of the evidence that IRS reduces malaria in such settings and due to concerns around feasibility and cost. When deciding whether IRS may be appropriate for prevention and control of malaria in humanitarian emergency settings, programmes should consider:

• whether the structures are suitable for spraying. Some shelters provided in emergency settings may not be suitable for application of insecticides, such as open-sided structures and those built from materials that affect the residual nature of the insecticides;
• whether the target coverage of IRS can be feasibly achieved in the setting;
• whether there are sufficient resources to cover the relatively high costs associated with an IRS programme. In such settings, transport of commodities to hard-to-reach areas, coupled with the need to quickly procure items and establish human capacity to deliver the intervention, is likely to incur higher costs than when deploying IRS in more stable settings. As with the deployment of IRS in more stable settings, WHO recommends that WHO-prequalified insecticides be selected for IRS use in humanitarian emergencies. It is important to ensure that the vector population is susceptible to the insecticide selected for spraying.

Practical Info In deciding whether to deploy IRS in emergency settings, as in more stable settings, consideration must be given to whether IRS is a suitable intervention for that setting, taking into account vector characteristics, human behaviour and available infrastructure. IRS is considered an appropriate intervention where the majority of the vector population feeds and rests indoors; the vectors are susceptible to the insecticide that is being deployed; people mainly sleep indoors at night; the majority of structures are suitable for spraying; and where high enough coverage can be achieved to provide community-level protection. Data will need to be collected to assess whether these criteria are met. Data on vector composition, density, behaviour and insecticide susceptibility prior to deploying IRS not only provide information as to whether IRS is suitable in that setting, but also provide baseline information against which changes can be detected and monitored. Combined with data on coverage, this information can be used to gauge the effectiveness and efficiency of IRS. However, there may be more limited capacity to regularly gather such data in humanitarian emergencies than in more stable settings. Data are also required on the structures present in humanitarian emergencies to assess whether they are amenable to IRS. Open-sided structures or those with surfaces constructed from materials that impact the residual nature of the spray may not be suitable. Initiating any IRS programme requires a well-defined management system to be established with dedicated human, logistical, transport and financial resources. Programmes and implementing partners should consider whether the logistical needs (acquisition of commodities and equipment, recruitment of personnel and transport) can be met in emergency situations with the available resources within the given timeframe. Timeliness is a key factor in obtaining the maximum benefits from IRS; the spray should be applied over the shortest period of time just prior to the onset of the transmission season. As with ITNs, instability in humanitarian emergencies may reduce the options for long-term planning, resulting in shorter lead times for establishing a programme and acquiring supplies and equipment than in more stable settings. If commodities and personnel have to be sourced at short notice, procurement costs may be higher. Costs may also increase if more expensive means of transport are required for deployment in more remote, less accessible areas or those affected by conflict. As with more stable settings, ensuring optimal coverage to provide community-level protection is critical. To support this community acceptance of IRS is essential. Given that in some humanitarian emergencies, the local language may differ to that of the affected population, consideration should be given to whether messaging needs to be adapted.