Hotspots of interactions
Emerging infectious disease outbreaks have been documented globally,
with hotspots identified in eastern North America, western Europe,
Japan, and Oceania (Jones et al. 2008). Numerous but more sparse
outbreaks have also been detected in South America outside of Amazonia,
sub-Saharan Africa, and southern Asia, many of which continue to pose
high risk for future outbreaks (Jones et al. 2008, Han et al. 2016,
Allen et al. 2017). Our results partially mirror these trends, with our
study identifying high numbers of reported human-wildlife interactions
in Brazil, China, India, Nepal, Uganda, and the United States. While
publication reports from these countries may be inflated due to
reporting bias, several of these countries have regions of growing
population densities where remaining natural lands continue to be
developed for agriculture (Deng et al. 2009), making them high-risk
areas for human-wildlife interactions. This overlap in patterns suggests
that our data can be used to identify regions with opportunities for
exposure to zoonotic pathogens, ultimately informing efforts to predict
future EID outbreaks.
Our results further indicate common reports of human-wildlife
interactions in agricultural portions of Africa and Asia akin to
previous studies on zoonotic disease emergence. Areas of southern and
eastern Asia and western and eastern Central Africa have previously been
identified as regions with high potential for zoonotic disease emergence
due to a combination of factors including high mammalian diversity,
large tracts of remaining forest threatened by increasing rates of
agriculturalization, and growing human populations (Grace et al. 2012,
Allen et al. 2017, Jagadesh et al. 2022). Human populations in these
regions of Africa and Asia with high rates of LUC may be exposed to an
exceptional diversity of wildlife, providing ample opportunities for
human interactions with novel wildlife pathogens (Allen et al. 2017).
For example, LUC via agriculturalization destroys forested areas,
leading to an increase in deforestation and creation of forest edges.
While human-wildlife interactions occur across all land cover types,
they are especially high in areas of intermediate LUC, where the
increase of edge facilitates high levels of contact among humans,
domestic animals, and wildlife (Kretser et al. 2008, Merkle et al. 2011,
Faust et al. 2018). The abundance of human-wildlife interactions, and
thereby potential for pathogen exposure, necessitates disease risk
surveillance in these regions.
Urban regions in parts of Europe and North America have also been
identified as high-risk areas for zoonotic pathogen transmission (Allen
et al. 2017) and our results show that the urbanizing areas on these
continents, and Oceania, are similarly hotspots for reports of
human-wildlife interactions. While some of this weight may be from
reporting bias, urbanizing areas in these continents are facing growing
human populations due to myriad reasons, including better healthcare for
resident populations, the increasing rate of rural to urban migration,
and movement from the global south to the global north (de Haas et al.
2019). This increase in human population often leads to local
environmental degradation, which can negatively affect the health of
local wildlife species and create new opportunities for human-wildlife
interactions that can lead to zoonotic pathogen transmission (Soulsbury
and White 2015, Plowright et al. 2017, Weber and Sciubbba 2019).
Subsequent reductions in environmental quality and local biodiversity
have ramifications for zoonotic disease emergence, as generalist
wildlife species able to cope with urbanization proliferate, increasing
pathogen prevalence as they move into areas left vacant by more
specialized species (Schmidt and Ostfeld 2001, Reusken and Heymann 2013,
Hough 2014, Hassell et al. 2017).
Many of geographic hotspots for zoonotic disease emergence have been
designated as such because of their high mammalian biodiversity (Allen
et al. 2017, Wilkinson et al. 2018). Previous work has demonstrated that
mammals represent a high risk for zoonotic pathogen transmission because
of their phylogenetic relatedness to humans and the wide breadth of
their ranges, which often facilitates close contact with humans
(Streicker et al. 2010, Han et al. 2016, Olival et al. 2017).
While all mammalian orders most
often involved in human-wildlife interactions are known to harbor
zoonotic pathogens, disease risk varies widely among these orders,
mostly due to variations in within-order diversity (Mollentze and
Streicker 2020). Groups like rodents (order: Rodentia) and primates
(order: Primates) have been thoroughly investigated for their zoonotic
pathogen potential due to their high species diversity and human
relatedness, compared to elephants for example (order: Proboscidea),
which have received comparatively less zoonotic pathogen surveillance
attention (Johnson et al. 2015, Han et al. 2016, Olival et al. 2017).
Our results show that disease surveillance efforts of these mammalian
orders are particularly warranted given their repeated interactions with
human and domestic animals stemming from growing rates of LUC (Johnson
et al. 2015, Han et al. 2016, Olival et al. 2017).