By the bioMérieux Connection Editors
The era of antibiotics, which began with the discovery of penicillin in 1928, substantially reduced the burden of infectious diseases. Paired with infrastructure developments such as plumbing and increased awareness and use of effective infection prevention practices, much of the world experienced enormous health gains. Between 1900 and 2020, global average life expectancy increased from 32 to 72 years. However, against this backdrop of health improvement over the past century, we have also seen new pathogens arise more frequently, leading to deadly local outbreaks, regional epidemics, and global pandemics.
There are many contributing factors that may raise the risks for new diseases and global pandemics: population dynamics along with economic, infrastructure, and healthcare inequalities; contact with and consumption of animals, both farmed and wild; the changing climate and its potential effects on the spread of infectious diseases; and the continuous development of antimicrobial resistance.
Population Dynamics & Poverty
Increasing populations can present problems in two ways. One is that as people spread out into new areas, they impinge on wildlife habitat, which increases the likelihood of contact with animals that can result in disease transmission. The other is that extremely dense populations can make it easier for pathogens to spread quickly.
Problems with economic inequality, inadequate infrastructure, and disparities in healthcare access may further hinder effective pandemic prevention and response in context of population increases. Economic inequality often leads directly to inadequate infrastructure for poor populations, creating problems with sanitation and plumbing that are responsible for the spread of infectious diseases. Lack of healthcare access, either because of insurance or because of a shortage of healthcare resources and infrastructure, creates an environment where people cannot receive care or cannot receive optimal care. This all allows infections to spread within communities—dense populations and animal contact due to urban sprawl then compound the problem.
Animal Contact & Consumption
According to the CDC, 6 out of every 10 infectious diseases are zoonotic, meaning they originate in animals. Because hunting and livestock farming both necessitate contact with animals, those two areas, as well as consumption of animal protein, represent major risks for novel pathogen and pandemic development.
Other examples of zoonotic diseases include but are not limited to: H1N1, which arose in context of pig farming; HIV/AIDS, which was first transmitted from apes to humans as a result of hunting; Ebola, which is transmitted via consuming infected wild animals; Lyme disease, which is carried by mammals and transmitted by ticks; malaria, Zika, and West Nile Virus, which have animal origins and are transmitted by mosquitoes; and SARS and MERS, which have both been linked to bats. As human populations increase and as people become wealthier, the demand for animal products, and the disease risks that result from contact with animals, will also increase.
Climate Change & Environmental Degradation
It is possible that climate change and environmental degradation may affect the spread of infectious diseases in a few different ways. However, because of the complex interplay of various factors—particularly economic growth and mitigating interventions—it is difficult to establish direct links between the spread of disease and climate change.
Still, concerns remain that climate may affect the prevalence and spread of a range of pathogens, including parasites and vector-borne diseases. In an article published in Infectious Diseases: Research and Treatment, researchers write that, “Accumulating evidence has begun to show that climate change is altering the spread and distribution of parasitic diseases and their associated vectors.” A report from a workshop convened by the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) suggested that environmental degradation and biodiversity loss may be linked to the spread of infectious diseases.
Global temperatures may contribute to a more hospitable environment for some pathogens and the vectors that spread them. Rising sea levels, extreme weather events, and protracted drought or repeated flooding could potentially drive dramatic population shifts and migrations in both the short term and long term. Extreme weather events, such as hurricanes, may displace thousands of people at one time, while rising sea levels may contribute to a slower but substantial migration away from coastal regions. It’s also possible that rising sea levels may lead to an increase in standing saline and brackish water in coastal areas, which harbor mosquitoes that can transmit infections. Droughts and repeated flooding may affect food production, leading to famine and social unrest that drives people from their homes. The conditions that population displacement creates, alongside increased population density and urban sprawl, may result in more opportunities for diseases to spread. Ultimately, more research is needed to better understand the complex ways that climate and other environmental factors impact human health.
Antimicrobial resistance has been called a “slow-moving pandemic.” Pathogens are constantly evolving in response to environmental pressures, including the antimicrobial agents we use to treat infections. Antimicrobial resistance can arise in any type of pathogen—bacteria, viruses, or fungi. Worldwide, it is estimated that 10 million people per year could die from resistant infections by 2050 if we do not act effectively to combat them. For context, that is almost equivalent to the entire population of Los Angeles (pop. approx. 12.4 million), and slightly more than the entire population of London (pop. approx. 9.0 million).
If we cannot effectively treat an infection, it becomes easier for it to spread. We have seen this treatment difficulty at work with COVID-19 because it is a novel pathogen, but this is also a problem for existing pathogens that acquire resistance mechanisms. Resistant pathogens can arise and spread in community settings, industrial settings, and healthcare settings. Additionally, each of the aforementioned issues—population dynamics, antimicrobial use associated with animal contact and consumption, and climate change—can all exacerbate antimicrobial resistance.
COVID-19 is also likely increasing the threat that antimicrobial resistance poses to human health in a few different ways. The authors of an article in The Lancet write that, “AMR might worsen under COVID-19 due to the overuse of antibiotics in humans, continuing misuse in agriculture, and the dearth of antimicrobials in the development pipeline. Competing global priorities are reducing AMR eradication activities, including measures for multidrug-resistant tuberculosis.”
Combating the Perfect Storm
The confluence of all of these issues—population dynamics and poverty, animal contact and consumption, climate change and environmental degradation, and antimicrobial resistance—creates conditions where deadly pandemics are not only possible, but probable. Mitigation will require a long-term, world-wide commitment to a One Health approach, with actions that address all risk factors.
Opinions expressed in this article are not necessarily those of bioMérieux, Inc.