The challenge of infectious diseases in an era of global changes

In recent decades, declines in mortality and morbidity, particularly childhood mortality, have been one of the great triumphs of public health. Greater access to care, such as therapeutics (including antibiotics), improved sanitation and the development of vaccines have been core drivers of this progress.

However, even as medical advances in the twenty-first century have spurred advances in population health, inequalities in access to these advances remain widespread between and within countries. Inequalities in health have existed for many decades and have led to unjust consequences in morbidity and mortality. The COVID-19 pandemic has played an important role in uncovering and amplifying numerous health inequalities that already existed within societies and between different population groups. This has led to disastrous and unjust consequences in mortality rates amongst minority ethnic groups, and vulnerable groups of society such as refugees, asylum seekers, and individuals from socioeconomically deprived backgrounds. Inequalities in health during COVID-19 have been exacerbated by interweaving risk factors and comorbidities which unfavorably magnify the disease burden and therefore this has been described as a co-occurring, synergistic pandemic for the more underprivileged communities. Reducing inequities in access to health care for infectious diseases around the world, and in underserved populations within countries, should be a priority in tackling pathogen emergence and spread.

While life expectancy continues to increase, and life years lost to infectious diseases decline, the new threat of infectious disease will likely come from emerging and re-emerging infections. Climate change, rapid urbanization, and changing land-use patterns will increase the risk of disease emergence in the coming decades. We have many reasons to take climate action to improve our health and reducing risks for infectious disease emergence is one of them. We don’t have direct evidence that climate change is influencing the spread of infectious diseases, but we do know that climate change alters how we relate to other species on Earth and that matters to our health and our risk for infections.

Climate change is occurring as a result of an imbalance between incoming and outgoing radiation in the atmosphere. As solar radiation enters the atmosphere, some of it is absorbed by the earth’s surface and reemitted as infrared radiation, which is then absorbed by greenhouse gases — primarily carbon dioxide, methane, and nitrous oxide — which result from the combustion of fossil fuels and which cannot be effectively removed from the atmosphere because of deforestation. This process generates heat. As the concentrations of greenhouse gases in the atmosphere have reached record levels, global temperatures have risen at a faster rate than at any time since records began to be kept in the 1850s, and temperatures are expected to increase by another 1.8 to 5.8°C by the end of this century. The hydrologic cycle will be altered since warmer air can retain more moisture than cooler air. Some geographic areas will have more rainfall, and some more drought, and severe weather events — including heat waves and storms — are expected to become more common. Because of rising temperatures and changing rainfall patterns, climate change is expected to have a substantial effect on the burden of infectious diseases that are transmitted by insect vectors and through contaminated water. Although governments must take the lead in tackling climate change, Global Alliance for Infections in Surgery believes that it is also our responsibility as members of the healthcare community to do our part. A continued uptick in global travel, trade, and mobility will transport pathogens rapidly, following emergence.

Technological change over the past two decades has dramatically lowered the cost of international travel, while demographic change has led to heightened demand for inexpensive flights. These changes to global connectivity will present unique risk factors for infectious disease spread, enabling pathogens to travel further and faster than ever before. The spread of SARS-CoV-2 has demonstrated the speed at which infections can spread across countries and around the world.

However, there are counterpoints to this trend: the rapid growth of connectivity observed in the early twenty-first century may stabilize, and structural changes wrought during the COVID-19 pandemic may persist. Efforts to develop universal vaccines could provide a monumental leap forward in tackling present and future infections. The swift development of the SARS-CoV-2 vaccine speaks to the efficacy of modern science in rapidly countering threats from emerging pathogens.

A changing world requires changing science to evaluate future risks from infectious diseases. Future work needs to explicitly address concurrent changes: how shifting patterns of demographic, climatic, and technological factors may collectively affect the risk of pathogen emergence, alterations to dynamics, and global spread. Increasing attention needs to be paid to pathogens currently circulating in both wild and domestic animal populations, especially in cases where agriculture is expanding into native species’ habitats and, conversely, invasive species are moving into populous regions due to climate change. As the battle against certain long-term endemic infections is won, institutional structures built to address these old enemies can be co-opted and adapted for emerging threats. At the same time, new technologies, including advances in data collection and surveillance, need to be harnessed. There is much recent innovation around surveillance, from reinterpreting information available from classic tools such as PCR to leveraging multiplex serology approaches to identify anomalies that might suggest pathogen emergence. In an increasingly connected world, the risk from infectious disease is globally shared. The COVID-19 pandemic, including the rapid global circulation of evolved strains, highlights the need for a collaborative, worldwide framework for infectious disease research and control.

Closely related to the challenge of infectious diseases in this era of global change is the global burden of antimicrobial resistance (AMR). AMR is among the top 10 global health threats. Resistance of bacteria to antibiotics is an urgent global public health and socioeconomic problem. Modern medicine depends on effective antimicrobial medicines, yet high rates of resistant infections across a broad range of microorganisms have been documented in all World regions. Despite many proposals and initiatives in recent decades, the world is failing to keep pace with microbes becoming increasingly resistant to available treatments. AMR is an unavoidable phenomenon that undermines the effectiveness of basic and modern medicine and is affecting people from birth to death everywhere in the world. Alexander Fleming warned of this in his 1945 Nobel prize lecture, and in the decades since, his warnings have proved extremely prescient.

More than 1.2 million people – and potentially millions more – died in 2019 as a direct result of antibiotic-resistant bacterial infections, according to the most comprehensive estimate to date of the global impact of AMR. The analysis of 204 countries and territories, published in The Lancet by Murray et al., reveals that AMR is now a leading cause of death worldwide, higher than HIV/AIDS or malaria. Disease burden was estimated in two ways: deaths caused directly by AMR (i.e., deaths that would not have occurred had the infections been drug-susceptible and therefore more treatable), and deaths associated with AMR (i.e., where a drug-resistant infection was implicated in deaths, but resistance itself may or may not have been the direct cause). Deaths caused by and associated with AMR were calculated for 204 countries and territories and reported for 21 global regions and seven super-regions. The analysis shows AMR was directly responsible for an estimated 1.27 million deaths worldwide, and associated with an estimated 4.95 million deaths, in 2019. HIV/AIDS and malaria have been estimated to have caused 860,000 and 640,000 deaths, respectively, in 2019. Deaths caused directly by AMR were estimated to be highest in Sub-Saharan Africa and South Asia, at 24 deaths per 100,000 population and 22 deaths per 100,000 population, respectively. AMR was associated with 99 deaths per 100,000 in Sub- Saharan Africa and 77 deaths per 100,000 in South Asia. In high-income countries, AMR led directly to 13 deaths per 100,000 and was associated with 56 deaths per 100,000. Of the 23 pathogens studied, drug resistance in six alone (E. coli, S. aureus, K. pneumoniae, S. pneumoniae, A. baumannii, and P. aeruginosa) led directly to 929,000 deaths and was associated with 3.57 million. One pathogen-drug combination – methicillin-resistant S. Aureus – directly caused more than 100,000 deaths in 2019, while six more each caused between 50,000 and 100,000 deaths. Across all pathogens, resistance to two classes of antibiotics often considered the first line of defense against severe infections – fluoroquinolones and beta-lactam antibiotics – accounted for more than an estimated 70% of deaths caused by AMR.

The etiology of AMR is multifaceted, and its consequences pose an impact across the globe. To adequately address AMR, it is necessary to take a ‘”One Health” approach with integrated actions across human, animal, and environmental health sectors. AMR is a complex and multidimensional problem, threatening not only human and animal health but also regional, national, and global security and the economy. Actions against AMR should focus firstly on local needs and national plans because each country is different. However, resistance is everyone’s problem and all countries have a role in solving the problem. The countries that have crafted inclusive national plans have been successful in controlling AMR. These approaches include cautious use of antibiotics, surveillance of antibiotics by employing the ‘One Health Approach’, advancement of health care setup, restricted drug promotion, consistent disease control strategies, and stewardship plans. On the other hand, these strategies demand patience and time to be organized. Furthermore, these require a comprehensive endorsement from the government authorities with ample funds. However, AMR poses a global challenge. No single country, however effective it is at containing resistance within its boundaries, can protect itself from the importation of AMR through travel and trade. Working alone is not sufficient and international partnerships to seek global solutions to tackle AMR are mandatory. By collaborating, there are opportunities for disseminating the best approaches for prevention and management. The global nature of AMR calls for a global response, both in the geographic sense and across the whole range of sectors involved. Nobody is exempt from the problem. AMR is universal, affecting anyone and everyone, at any age and in any country and misuse of antibiotics is worsening the situation globally. Urgent action is needed. The COVID-19 pandemic shows that despite all of our medical advances, we remain incredibly vulnerable to infections for which we have no therapies. However, it shows that if sufficiently motivated, we can make huge changes in short time frames.

The lesson learned from the COVID-19 pandemic has been that the world was woefully under-prepared for effectively managing emerging public health threats. AMR should be recognized as one of them – an ongoing, insidious pandemic that develops rapidly but more silently compared to COVID-19.

With the growing and urgent threat posed by antibiotic-resistant bacteria, there is truly no time to waste. Common sense and coordinated solutions need to be initiated immediately, and the global community must at the same time work to increase the attention, and action commensurate with the scale of what’s at stake.