Global biogeography of human infectious diseases

Abstract

The distributions of most infectious agents causing disease in humans are poorly resolved or unknown. However, poorly known and unknown agents contribute to the global burden of disease and will underlie many future disease risks. Existing patterns of infectious disease co-occurrence could thus play a critical role in resolving or anticipating current and future disease threats. We analyzed the global occurrence patterns of 187 human infectious diseases across 225 countries and seven epidemiological classes (human-specific, zoonotic, vector-borne, non–vector-borne, bacterial, viral, and parasitic) to show that human infectious diseases exhibit distinct spatial grouping patterns at a global scale. We demonstrate, using outbreaks of Ebola virus as a test case, that this spatial structuring provides an untapped source of prior information that could be used to tighten the focus of a range of health-related research and management activities at early stages or in data-poor settings, including disease surveillance, outbreak responses, or optimizing pathogen discovery. In examining the correlates of these spatial patterns, among a range of geographic, epidemiological, environmental, and social factors, mammalian biodiversity was the strongest predictor of infectious disease co-occurrence overall and for six of the seven disease classes examined, giving rise to a striking congruence between global pathogeographic and “Wallacean” zoogeographic patterns. This clear biogeographic signal suggests that infectious disease assemblages remain fundamentally constrained in their distributions by ecological barriers to dispersal or establishment, despite the homogenizing forces of globalization. Pathogeography thus provides an overarching context in which other factors promoting infectious disease emergence and spread are set.

Disease biogeography: spatial and temporal analyses of infectious disease burden at the country-level scale provides new insights and challenges

“…At first glance, this finding may be unsurprising as human infectious disease burden can be correlated with increases in the number of potential hosts (Jones et al 2008, Dunn et al 2010, Murray et al 2015. However, this finding also conflicts directly with the dilution effect hypothesis (Keesing et al 2010) and the decoy hypothesis (Stensgaard et al 2016), which suggests that increases in the number of hosts is likely to reduce subsequent disease risk in alternative hosts.…”

“…This is particularly true for regions/countries that do not have strong public health programs and often for Neglected Tropical Diseases (NTDs), which by their nature are understudied and poorly represented in health surveys (Hotez et al 2014, Stensgaard et al 2017. Understanding what drives disease burden is also challenging because diseases can be impacted by ecological, economic, and demographic factors (Sachs and Malaney 2002, Jones et al 2008, Murray et al 2015, Stephens et al 2016. Therefore, studies that try to identify global drivers of infectious diseases must find ways to deal with data limitations and factors that are operating at different spatial and temporal scales.…”

Mammalian biogeography and the Ebola virus in Africa

“…Recent biogeographical analyses have highlighted the importance of potential reservoirs (animals that can harbour the pathogen indefinitely with no ill effects) in explaining the spatial assemblage of human infectious diseases worldwide (Murray et al. ). Biogeography has contributed broadly to the questions of infectious disease ecology, management, and surveillance (e.g.…”

Homologous Recombination and Xylella fastidiosa Host–Pathogen Associations in South America

“…Therefore, broadly observed patterns serve as starting points when evaluating factors associated with emerging diseases caused by related pathogens. Quantitative analyses of databases and published literature have provided important insights on factors, as well as pathogen groups and potential geographical hotspots, associated with emerging animal and human diseases (Murray et al 2015). A very limited number of similar studies are available for plants (Anderson et al 2004) but plant diseases emerge due to a variety of factors, from breakdown of host plant resistance via pathogen adaptation (Croll and McDonald 2012) to the introduction of new insect vectors (Almeida and Nunney 2015).…”