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Review
. 2022 Apr;20(4):193-205.
doi: 10.1038/s41579-021-00639-z. Epub 2021 Oct 13.

Infectious disease in an era of global change

Affiliations
Review

Infectious disease in an era of global change

Rachel E Baker et al. Nat Rev Microbiol. 2022 Apr.

Abstract

The twenty-first century has witnessed a wave of severe infectious disease outbreaks, not least the COVID-19 pandemic, which has had a devastating impact on lives and livelihoods around the globe. The 2003 severe acute respiratory syndrome coronavirus outbreak, the 2009 swine flu pandemic, the 2012 Middle East respiratory syndrome coronavirus outbreak, the 2013-2016 Ebola virus disease epidemic in West Africa and the 2015 Zika virus disease epidemic all resulted in substantial morbidity and mortality while spreading across borders to infect people in multiple countries. At the same time, the past few decades have ushered in an unprecedented era of technological, demographic and climatic change: airline flights have doubled since 2000, since 2007 more people live in urban areas than rural areas, population numbers continue to climb and climate change presents an escalating threat to society. In this Review, we consider the extent to which these recent global changes have increased the risk of infectious disease outbreaks, even as improved sanitation and access to health care have resulted in considerable progress worldwide.

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Conflict of interest statement

The authors declare no competing interests.

Figures

Fig. 1
Fig. 1. Human connectivity and infectious disease outbreaks in premodern and modern times.
a | Examples of epidemic periods associated with different eras of human transportation (land, maritime and air travel) are shown. Overland trade networks and war campaigns are thought to have contributed to multiple epidemics in the Mediterranean in late classical antiquity (green), beginning with the Antonine plague, which reportedly claimed the life of the Roman emperor Lucius Verus. Maritime transportation (red and grey) leading to European contact with the Americas and the subsequent Atlantic slave trade resulted in the importation of Plasmodium falciparum malaria and novel viral pathogens. In modern times, air travel (purple) resulted in the importation of severe acute respiratory syndrome (SARS) coronavirus to 27 countries before transmission was halted. b | In recent years, increases in air travel, trade and urbanization at global (left) and regional (right) scales have accelerated, indicating ever more frequent transport of people and goods between growing urban areas (source World Bank). c | Log deaths from major epidemics in the twenty-first century (source World Health Organization). d | Disability-adjusted life years lost from infectious diseases (source Our World in Data). MERS, Middle East respiratory syndrome; NTD, neglected tropical disease.
Fig. 2
Fig. 2. Impacts of urbanization on infectious disease.
Interactions between urbanization and infectious disease are complex, with increased urbanization driving both positive and negative changes to global disease burden.
Fig. 3
Fig. 3. Effects of climatic, technological and demographic change on disease emergence, dynamics and spread.
The table summarizes select recent global changes (rows) and their impacts on disease emergence, local-scale dynamics and global spread (columns). An example susceptible (S), infected (I), recovered (R) model is shown, where β represents the transmission rate and γ is the recovery rate.
Fig. 4
Fig. 4. Mapping changes to travel and climate.
a | The global international air travel network expanded substantially from 1933 to 2020 (data from WorldPop and ref.). b | Average monthly maximum temperature in 1970–2000) and difference between 2070–2100 and 1970–2000 averages (data from WorldClim, Shared Socioeconomic Pathway 3 (SSP3)). c | Population projections under SSP3 in 2010 and relative population change projected until 2100 (source NASA Socioeconomic Data and Applications Center (ref.)). Part a adapted with permission from ref., OUP.

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