Background

The WHO defines an emerging infectious disease (EID) as ‘one that either has appeared and affected a population for the first time, or has existed previously but is rapidly spreading, either in terms of the number of people getting infected or to new geographical areas’.1 Over 60% of EIDs are zoonotic, having crossed over from animals to humans by a process called spillover.2 Recent outbreaks due to novel zoonotic infectious diseases include COVID-19, MERS-CoV, Ebola virus disease, Zika virus disease, SARS-CoV and novel influenza viruses.3–5 Empirical evidence suggests that many systemic societal and social factors contribute to the appearance of EIDs including urbanisation, climate change, increasing travel and trade, human population growth, human behaviour and the emergence of antimicrobial resistance.4 6

Even though EIDs are known to cause a substantial threat to human life and can impose significant economic burden, Fauci and Morens6 argue that the behaviour of such diseases can be predicted and mitigated.6 Public health history provides solid evidence that public health measures, including clean water, sanitation, vaccinations and antibiotics, have been effective in decreasing the burden of EIDs.6 In more recent history, many countries around the world have invested in increasing national and international communicable diseases control capacities and resources in order to prepare and respond to the next potential pandemic caused by EIDs.7 However, due to the novelty of these diseases, there are considerable gaps in our knowledge for the prevention and control of EIDs.4 5

From its early origins in the middle of the last century, systems science has evolved its own distinguishable academic identity and a corpus of related scientific literature devoted to the subject. Since then, it has offered academics and practitioners from a variety of fields a number of different approaches and methods for helping better describe and solve ‘complex’ social, technological, ecological and organisational problems. By ‘complex’ we mean having features of ‘complexity’ as found in complex adaptive systems. Those features include multiple interacting components, non-linear relationships and feedback loops between them that might be moderated or synergistic with other system elements. In addition, interactions across multilayered contexts may induce emergent outcomes at various levels that cannot be predicted from relationships observed at any single level.8

Those working in this field have appropriated a number of methods and tools9 and while many of these have roots in computer science, operational research and simulation, others are alternatively branded as ‘soft systems’ methods that invoke paradigmatic systems thinking.8 This may often take us a long way towards a solution by allowing us to see our problem as a feature of a complex adaptive system rather than focusing on a single cause and effect.8 It does so by helping us explore the purpose, behaviour and dynamics of the system’s elements and what connects them.10 By mapping the patterns of behaviour within a system and what generates them, the use of systems-oriented methods and tools can help us see the ‘bigger picture’ and better appreciate where the sweet spots for intervention might lie to achieve desirable outcomes.8 9

Systems thinking and the associated tools of systems dynamics have made inroads into healthcare management.9 Since many of the big issues affecting public health are easily seen among what are known as ‘wicked problems’, systems thinking has begun to take root in public health.11 For example, Rutter and colleagues12 advocated the use of systems science to inform policy debates and to help policymakers find more holistic answers to public health problems. They argued that many public health questions are merely features of complex adaptive systems; therefore, linear or straightforward solutions might not be sustainable,12 echoing Bircher and Hahn.13–15

In 1995, Wilson argued that EIDs represent a complex and dynamic issue, the public health consequences of which are not merely caused by the infectious agent itself. Other key aspects like human behaviour, environmental, geographical and economic factors contribute to the complexity that defies simplistic solutions,16 a sentiment which Fauci and Morens echoed in 2012.6 Thus, more systemic measures are necessary to address the complexity surrounding EIDs to provide sustainable and adaptive solutions. Thus, such measures might invoke systems-oriented methods, like systems maps, causal loop diagrams and systems dynamics, to demonstrate the links between different elements of a system that might otherwise seem unrelated or be overlooked when studied with conventional methods.

There have been some previous attempts to use systems-oriented approaches in infectious disease research, including, for example, Ebola virus disease, HIV, tuberculosis, influenza and vaccine uptake.17 Systems science methods were also recommended by Shi et al, who used examples of disease transmission prediction for influenza A H1N1 in Hong Kong and malaria in Yunnan Province in China, to provide policymakers with a better understanding of how to enhance surveillance and preparedness.18 Lee et al provided another example for using systems science, mapping the elements that make up the vaccine manufacturing and distribution system; thereafter, they used multiple systems models to inform policymakers of the best ways to maximise the benefit and reduce wasted resources.19 Nevertheless, while interest has been growing, there has been no systematic attempt to scope the charted and uncharted ground over which systems science methods and systems thinking can help societies manage EIDs.

Before writing this protocol, a comprehensive search of databases for scoping or systematic reviews on the topic was conducted. Resources used at this stage included Scopus, the Joanna Briggs Institute (JBI) Database of Systematic Reviews and Implementation Reports, the Cochrane Database of Systematic Reviews, PubMed, Evidence for Policy and Practice Information and Epistemonikos. To the best of our knowledge, no scoping or systematic reviews exploring the role of systems approaches to the control of EIDs have been published (up to the time of writing).

Therefore, this review has the potential to inform researchers and policymakers about innovative ways to prevent and control EIDs at global, national and regional levels. It can provide evidence on how systems-oriented approaches can complement classical public health approaches to the prevention and control of EIDs. Researchers can use this review as a precursor to a more systematic review on the topic.

This review has two objectives. First, to identify the main concepts and characteristics of systems-oriented approaches, as applied to EIDs. Second, to systematically map the evidence for the use of systems-oriented methods in controlling infectious diseases and identify gaps in knowledge.

Following the Population, Concept and Context criteria provided in the JBI framework for clearly delimiting the research question,20 this review will focus on human populations; the concept will be systems-oriented methods; while the context is related to EID preparedness and response.

This review will have one main question and multiple subquestions. Those questions might go through further development and change when conducting this study as the reviewers develop a deeper understanding of the topic.

The research question is how can systems-oriented approaches be used for prevention and control of emerging infectious diseases?

Subquestions include:

• What were the main systems-oriented concepts in these works? Are they defined and operationalised consistently?

• What were the systems-oriented questions?

• What types of elements were considered as part of the system? How were they defined?

• What were the methods used?

• How were stakeholders involved (if any)?

• What are the key insights provoked by the use of the systems-oriented approach?

• What limitations and potential developments for the use of systems methods in controlling EIDs were pointed by other researchers?