Facing the future of respiratory virus surveillance: “The mosaic surveillance framework”

Abstract It is impossible to address the many complex needs of respiratory virus surveillance with a single system. Therefore, multiple surveillance systems and complementary studies must fit together as tiles in a “mosaic” to provide a complete picture of the risk, transmission, severity, and impact of respiratory viruses of epidemic and pandemic potential. Below we present a framework (WHO Mosaic Respiratory Surveillance Framework) to assist national authorities to identify priority respiratory virus surveillance objectives and the best approaches to meet them; to develop implementation plans according to national context and resources; and to prioritize and target technical assistance and financial investments to meet most pressing needs.

Surveillance Framework) to assist national authorities to identify priority respiratory virus surveillance objectives and the best approaches to meet them; to develop implementation plans according to national context and resources; and to prioritize and target technical assistance and financial investments to meet most pressing needs. Population expansion, travel patterns, and global trade also present an ongoing risk of new pandemics and a continuing need to strengthen early warning surveillance. To face these challenges, countries must now increase the number of effective surveillance approaches to address multiple surveillance objectives and extend partnerships for surveillance and collaborative analyses of data across sectors. Doing so will improve data for decision-making during interpandemic periods and to help ensure that respiratory virus surveillance is both timely and scalable in emergencies. WHO Member States have requested a coordinated approach to the sustainable monitoring of respiratory viruses of epidemic and pandemic potential. 1 For respiratory virus surveillance to function during interpandemic periods and to be resilient to inform decisionmaking during times of emergency, surveillance systems must be wellsuited to the objectives that they are being implemented to address.
Fit-for-purpose surveillance will produce actionable and policyrelevant information that will engender trust and demonstrate their value for money, increasing commitment by public health authorities to invest in surveillance over time. Conversely, poorly targeted or inefficient surveillance systems may generate sub-optimal or misleading data for decision-making, and not be perceived as cost-effective to sustain or scale in emergencies. Comprehensive surveillance for respiratory viruses involves detecting and assessing emerging or re-emerging pathogens; monitoring epidemiological and clinical characteristics of illness associated with infections and the virological characteristics of respiratory viruses currently in circulation; and informing the use of human health interventions ( Figure 1). As it is impossible to address all these objectives with a single surveillance system, multiple systems and complementary investigations 2 must work together to address the many information needs of policy makers. In essence, each system or study serves as a tile in a "mosaic", and only when viewed together will they provide the complete and understandable picture of the human health risk and impact associated with epidemic and pandemic respiratory viruses in circulation.
The COVID-19 pandemic generated innovations to support surveillance, including those related to improved point of care or selftest diagnostic technologies, environmental surveillance, community participatory surveillance, and the rapid improvement in global genomic surveillance. 3 To inform longer-term surveillance planning, this framework considers some of the benefits, limitations, and most appropriate applications of these innovations to inform possible surveillance strategies.
Critically, national surveillance strategies must be directed by the objectives and information needs of local authorities, locally available resources, and feasibility within the populations under surveillance.
Surveillance methods that can help address needed objectives include but are not limited to event-based surveillance in health-care facilities, the community, and at the animal-human interface; sentinel surveillance using standardized case definitions and integrated laboratory testing; strong networks of connected public health and clinical laboratories; efficient and comprehensive nationally notifiable disease surveillance systems; targeted surveillance in specific high-risk F I G U R E 1 Surveillance domains and associated objectives for respiratory viruses of epidemic and pandemic potential.
The vision and aims of the mosaic surveillance framework. settings and vulnerable populations; sustained health-care capacity monitoring; and enhanced clinical surveillance, among others.
Surveillance systems need to be complemented with high-quality and timely outbreak investigations and studies to obtain information not routinely available from ongoing systems.
There are also several structural or enabling factors that are critical to the success of any sustainable surveillance. These include strong governance and leadership, sustainable financing and workforce, and integration of data standards and appropriate innovations to promote timely and collaborative analyses of surveillance information from multiple sources. Given the complexity of the current respiratory surveillance landscape, national authorities now need an evidence-based framework to help their countries rapidly ( Figure 2): • identify priority respiratory virus surveillance objectives; • identify the surveillance approaches that have been used to meet these objectives; • prioritize required enhancements of existing surveillance; • develop implementation plans according to the national context, resources, and needs; 2005, specifically the core capacity requirements for surveillance and response and the National Action Plans for Health Security, 5 and will be adapted if the ongoing discussion related to the revision of the IHR (2005) requires it. Importantly, this framework is a conceptual structure that underpins and supports current initiatives and does not supersede any existing global or regional normative surveillance guidance. Rather, it is intended to place the systems represented by existing guidance into a context where they may address the objectives for which they are best intended. The framework presents appropriate uses of existing systems for respiratory virus surveillance and refers to existing global and regional surveillance-specific guidance and operating procedures wherever they exist.

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The specific tools to help countries implement the mosaic surveillance framework will include those to help prioritize respiratory surveillance objectives, map existing systems to priority objectives; and to identify priority enhancements needed. However, associated tools will also help national authorities consider the need to strengthen broader enabling structures for surveillance in their countries.
Our vision is that all countries develop well-coordinated mosaics of multiple fit-for-purpose surveillance approaches that address priority surveillance objectives for influenza, SARS-CoV-2, RSV, and other respiratory viruses of epidemic and pandemic potential according to country context. Respiratory viruses serve as a prototypical example of the way surveillance systems can work together resiliently to provide a comprehensive picture of disease emergence, spread, and impact. There are several respiratory viruses that have important commonalities in terms of virological, epidemiological, and clinical surveillance approaches. However, there are areas where this framework has applicability beyond respiratory viruses and, in some cases, beyond respiratory pathogens. The next respiratory pandemic remains imminent, and the time is now to apply lessons learned to assure that