Surprising study suggests urbanization may reduce global infectious disease risk

In a recent meta-analysis published in the journal Nature, Researchers used more than 2,938 published observations to uncover the drivers of global change that are most contributing to the global surge in infectious diseases in both humans and other non-human organisms. are collated, analyzed, and discussed. Their research reveals that biodiversity loss, species introduction, climate change, and chemical pollutants directly or indirectly increase the risk of infectious diseases. In contrast to previous reports, deforestation and forest fragmentation do not play a significant and generally minor role in the observed host-parasite interactions. Surprisingly, urbanization was found to be associated with reduced risk of infectious diseases.

These findings provide important insights into the determinants of infectious diseases and partially explain the increasing prevalence of infectious diseases around the world. These can be used to inform disease control and surveillance policies worldwide, allowing policy makers to make informed decisions about the most efficient investment of human resources to improve future disease outcomes. Helpful.

study: A meta-analysis of global drivers of change and infectious disease risks.. Image credit: Francesco Scatena / Shutterstock

The impact of anthropogenic change on global health

The crowning glory of modern human society includes advances in health care and disease management. Unfortunately, reports and scientific publications reveal that the prevalence of emerging infectious diseases is increasing at an alarming rate, both in human and non-human host-parasite interactions. . Previous research suggests that socio-economic, environmental, and ecological factors driving global change, most of which are anthropogenic, are significantly associated with the observed spike in disease risk. I am. However, these studies typically focus on one or a few factors and lack an overall overview of which factors have the most significant impact and therefore require significant investment in management. I am.

“Although there are many individual studies on infectious disease risk and environmental change, as well as comprehensive studies on how factors of ecosystem change affect infectious diseases, the number of infectious diseases in plants, animals, and humans worldwide There is a lack of formal meta-analyses examining how it varies across the board.”

About meta-analysis

In this meta-analysis, researchers collated the available literature on the link between host-parasite interactions and the drivers of global, typically human-mediated, change across plants, animals, and humans. The purpose was to analyze the results. They also attempt to determine the relative impact of each factor on global infection risk and whether these associations are generalizable or context-dependent. To accomplish this, the researchers analyzed five global topics: biodiversity, landscape change, climate change, chemical pollution, and species introductions from three scientific literature repositories: Web of Science, PubMed, and Scopus. We collected publications related to any of the factors of change.

Research should be reviewed in terms of publication type (book chapters, gray literature, conference proceedings, reviews) and language (non-English publications may be translated into English during the review process), as long as the studies are peer-reviewed and concise conclusions are drawn. ) was included regardless of the translation. On the impact of global change drivers of interest on pathogens/parasites. Data collection included extraction of disease endpoint indicators of global change (e.g., variance, standard deviation), subcategories of global change drivers, relevant host and pathogen species, and other quantified host or pathogen characteristics. Contains definitions. Obvious spelling errors were manually corrected before inclusion in the meta-analysis pipeline.

When a single pathogen could infect multiple closely related hosts, the different hosts were replaced by manual assignment of a higher taxonomic order. As some hosts and parasites have undergone taxonomic revisions since their respective research publications, the Global Names Resolver platform (Encyclopedia of Life) was used to correct and update such revisions. .

Meta-analyses were performed in R software (v.4.2.2) using multiple multilevel mixed-effects models. Because the data were observed to have a large number of effect sizes (sometimes including multiple non-independent observations within the same study), all included mixed-effects models included study-level and observation-level variables. was corrected using the effect and then robust variance was applied. estimator.

“We first estimated the overall heterogeneity explained by the overall grand mean and random effects terms. We then tested the impact of broad global change drivers on disease. Third, we conducted a meta-analytic model with global change drivers as moderators to test whether the subfactors that drive global change differentially impact disease. We conducted a meta-analytic model using the driving subfactors as moderators. Fourth, we sought to test the context dependence of the effects of global change drivers on disease.”

Publication-specific bias was assessed using funnel plots, multilevel meta-regions, year of publication, and moderator variables (the latter also serving as a test for time-lag bias).

Research results and conclusions

The literature screening process identified 972 publications containing 2,938 observations of 1,006 parasite species, 480 host species, and 1,497 host-parasite interactions. Encouragingly, all continents (except Antarctica) are well represented in the final dataset, with both high-income and low-to-middle income countries (LMIC) represented by each identified driver. More than 20 field studies have been conducted in each country. The only exceptions for six and three LMIC publications were chemical contamination and introduced species, respectively.

The results of this meta-analysis highlight that biodiversity loss, chemical pollution, climate change, and alien/introduced species are the most important determinants of increased global disease risk. These findings were found to be consistent across both human and non-human host parasitic diseases, although highly context dependent.

“Endpoints from parasites with complex life cycles, such as large parasites and vector-borne pathogens, decrease more with habitat loss/change compared to endpoints from simple parasites; They increased further with changes in biodiversity and less strongly in response to alien species. Life cycles changed and ectoparasites increased more in response to alien species compared to endoparasites. .”

Despite individual publications suggesting that deforestation and forest fragmentation are major drivers of global infection risk, the current meta-analysis suggests that these factors play a minor role in the observed disease prevalence. It turns out that they often play an unimportant role. Surprisingly, we found that urbanization is associated with reduced infectious disease risk, but the mechanisms supporting these observations require additional research before considering urbanization as a strategy for infectious disease control. be.

In summary, the present meta-analysis identifies and highlights the global drivers of change that are most contributing to the increased prevalence of diseases across plants, non-human animals, and humans. This provides policymakers with the knowledge they need to allocate limited resources to achieve ideal disease risk reduction worldwide.