Abstract
The human population is growing, requiring more space for food production, and needing more animals to feed it. Emerging infectious diseases are increasing, causing losses in both human and animal lives, as well as large costs to society. Many factors are contributing to disease emergence, including climate change, globalization and urbanization, and most of these factors are to some extent caused by humans. Pathogens may be more or less prone to emergence in themselves, and rapidly mutating viruses are more common among the emerging pathogens. The climate-sensitive vector-borne diseases are likely to be emerging due to climate changes and environmental changes, such as increased irrigation. This review lists the factors within pathogens that make them prone to emergence, and the modes of transmission that are affected. The anthropogenic changes contributing to disease emergence are described, as well as how they directly and indirectly cause either increased numbers of susceptible or exposed individuals, or cause increased infectivity. Many actions may have multiple direct or indirect effects, and it may be difficult to assess what the consequences may be. In addition, most anthropogenic drivers are related to desired activities, such as logging, irrigation, trade, and travelling, which the society is requiring. It is important to research more about the indirect and direct effects of the different actions to understand both the benefits and the risks.
Generated Summary
This review article examines the consequences of human actions on the risks of infectious diseases, focusing on the complex interplay between anthropogenic changes and disease emergence. It explores various factors contributing to the rise of infectious diseases, including climate change, globalization, urbanization, and human activities such as deforestation, irrigation, and livestock intensification. The study reviews existing literature to provide a framework for evaluating the risks associated with these environmental changes and their impact on disease transmission and dynamics. The review considers the factors within pathogens that make them prone to emergence and the modes of transmission that are affected. The work encompasses a broad range of topics related to infectious diseases, including zoonoses, ecosystem changes, disease dynamics, and food security.
Key Findings & Statistics
- The human population is over 7 billion.
- Infections contribute to more than 20% of the global burden of disease, and over 70% in Africa.
- The Spanish flu pandemic (1918-1920) caused an estimated 50-100 million deaths.
- Rinderpest caused massive death in livestock and the subsequent death by starvation of almost two-thirds of the East African Massai population.
- The potato blight caused the Irish potato famine, reducing the Irish population by 25%.
- In Thailand, deaths from infections decreased to one-fifth from 1958 to 1997, then increased again, mainly due to HIV.
- The World Bank estimates direct costs of zoonotic outbreaks in the last century have exceeded US$20 billion, with indirect costs of US$200 billion.
- It is estimated that 44% of the diseases considered emerging in humans are viral.
- Economic losses from white-nose syndrome in bats may cause agricultural losses of at least US$3.7 billion per year.
- Vector-borne diseases constitute around 23% of the infections considered emerging.
- Increased irrigation in agricultural areas is necessary for 40% of global crop production.
Other Important Findings
- Emerging infectious diseases (EIDs) are on the rise, causing significant losses in human and animal lives, and substantial costs to society.
- Many factors are contributing to disease emergence, including climate change, globalization, and urbanization, and most of these factors are to some extent caused by humans.
- The article identifies factors within pathogens that make them prone to emergence and the modes of transmission that are affected.
- Anthropogenic changes directly and indirectly increase susceptible or exposed individuals or increase infectivity.
- Most anthropogenic drivers are related to desired activities like logging, irrigation, trade, and travel.
- Definitions of EID vary, but generally include diseases with increasing incidence, geographic spread, or the ability to infect new species or populations.
- Viruses and protozoa have the highest proportions of emerging pathogens. Zoonotic pathogens are more likely to emerge than non-zoonotic ones.
- Hot spots of EID often have intensified agricultural systems, especially livestock keeping.
- Small-scale farmers may be disproportionately affected by EID.
- Factors within pathogens, such as the capacity to evolve through mutations, are important for disease emergence.
- RNA viruses are prone to emergence due to rapid replication and high mutation rates.
- Bacteria and rickettsia constitute 38% of human pathogens, and 30% of the emerging pathogens in humans.
- The spread of antibiotic resistance in bacteria is a major concern.
- Fungal infections are emerging among plants, animals, and humans.
- Parasitic diseases appear to be increasing, with many helminthic infections being zoonotic.
- Globalization increases the transfer of pathogens into new areas, but is essential for trade and economies.
- Deforestation and reforestation have varied effects on disease emergence.
- Increased irrigation can increase vector habitats and vector-borne diseases.
- Livestock intensification can be associated with both increased and decreased disease risks.
- Hunting and bushmeat consumption are linked to increased disease risks.
Limitations Noted in the Document
- The review acknowledges the difficulty in formulating policies for risk reduction due to a lack of understanding of causality, trade-offs, and externalities of decisions.
- The paper does not offer any new data or original research. It is solely based on reviewing existing literature.
- The review’s scope is broad, covering various drivers of disease emergence; this breadth may prevent an in-depth analysis of any single factor.
- The stochastic nature of disease emergence means that similar scenarios may not produce identical outcomes, complicating predictive modeling.
- The complexity of interactions between anthropogenic changes and pathogen dynamics makes it challenging to fully assess the consequences of specific actions.
Conclusion
The study emphasizes the need for a multidisciplinary approach in research and policymaking to understand how human actions affect disease emergence. Disease control and monitoring should extend beyond medicine and epidemiology to include social, environmental, and economic values. The authors highlight that many drivers of disease are linked to activities promoted by governments and society due to their perceived benefits. The article underlines that the impacts of globalization, deforestation, irrigation, livestock intensification, and hunting on disease emergence are complex and multifaceted, often involving both positive and negative consequences. The importance of considering the varying priorities of different cultures and the need for compromises and trade-offs when addressing disease risks are central themes. The study suggests that top-down interventions may be counterproductive if they do not account for local population incentives. The research stresses the need to assess the direct and indirect effects of different actions to fully comprehend both the advantages and risks associated with human activities. The authors advocate for a more comprehensive understanding of the intricate relationships between ecosystems, human actions, and disease dynamics to inform effective public health strategies and promote sustainable practices.