Volume 196 - Issue 5
The 20th century re-emergence of epidemic infectious diseases: lessons learned and future prospects
Author: Duane J Gubler
Med J Aust 2012; 196 (5): 293-294. || doi: 10.5694/mja12.10104
Published online: 19 March 2012
Published online: 19 March 2012
Decades of population growth, globalisation and complacency are driving new epidemics. Unexpected plagues of epidemic infectious diseases have entered human history for centuries, often with devastating consequences. With good public health and the advent of new drugs, vaccines and insecticides in the middle of the 20th century ...
Decades of population growth, globalisation and complacency are driving new epidemics
Unexpected plagues of epidemic infectious diseases have entered human history for centuries, often with devastating consequences. With good public health and the advent of new drugs, vaccines and insecticides in the middle of the 20th century, most major infectious diseases affecting human health were effectively controlled. However, epidemic infectious diseases have dramatically re-emerged in the past 30 years. The frequency of epidemics caused by newly emerging and re-emerging pathogens, and the likelihood of rapid global spread, have also increased, as illustrated by high-profile epidemics caused by zoonotic pathogens in recent years.
The victories of the past culminated with the war on infectious diseases being declared won in the 1960s.1 This was followed by a period of increasing apathy and complacency in the second half of the 20th century. A new paradigm of surveillance and emergency response became the recommended method for controlling epidemic infectious diseases. Resources were redirected to other public health priorities such as non-communicable diseases, new antibiotic development was essentially ceased, and an era of growing environmental activism made it increasingly difficult to control vector-borne and zoonotic diseases.2-5 As a result, public health infrastructure and hygiene deteriorated globally to the point where they provided little protection against infectious diseases.
Unrecognised by infectious disease experts was the coincident emergence of global trends that would ultimately drive the emergence of many epidemic infectious diseases, including those that had been effectively controlled. These trends included unprecedented population growth, and unplanned urbanisation and globalisation; the latter two driven by post-World War II economic growth.2-6 The jet aeroplane provided the ideal mechanism to rapidly transport people, animals and pathogens to new geographic regions. Thus began a global re-emergence of epidemic infectious diseases that is continuing today.3,5
Unfortunately, few countries, especially those resource-poor tropical countries where most newly emergent diseases will originate in the future, have the public health capacity and capability to address this threat. With few exceptions, most infectious pathogens are ignored until an epidemic occurs, at which time local and international health agencies move into emergency response mode, which is almost always too little and too late to have any impact on transmission. This type of crisis mentality is very dangerous in an era when highly transmissible pathogens can move rapidly around the globe. Two such epidemics in the past 18 years have affected global commerce. The first was the 1994 Indian pneumonic plague epidemic, which did not spread out of India.7 The 2003 severe acute respiratory syndrome (SARS) epidemic was more devastating, costing the global economy an estimated US$40–$50 billion.8 Neither of these epidemics were major public health crises in terms of number of cases or deaths, but, because of inadequate laboratory and epidemiological capacity, they caused panic and chaos. Both epidemics threatened global economic and public health security. Future epidemics will likely have even greater global public health and economic impact. Pandemic (H1N1) 2009 influenza had the potential to cause such chaos, as the virus was highly transmissible and spread around the world in just a few months. Fortunately, however, the illness associated with the virus was mostly mild and did not cause the panic and alarm of a more virulent virus.
Many lessons about infectious diseases and their resilience in the face of defeat have been learned in the past three decades. The most important lesson is that global trends (population growth, unprecedented urban growth, and globalisation) combined with lack of effective public health have been the principal drivers of the dramatic expansion of epidemic infectious diseases. Rural-to-urban migration patterns increase the probability of exotic rural pathogens being introduced to crowded urban areas, and modern transportation and globalisation greatly increase the probability of rapid geographic spread. A second lesson learned is that even though most resource-poor countries list infectious diseases among their top health priorities, very few have invested in the public health infrastructure needed to effectively prevent and control them. A third lesson is that effective threat reduction and containment of epidemic diseases that have the potential to spread rapidly will require early detection and identification of the pathogens in the countries where they emerge. This will require much better laboratory and epidemiological capacity and capability in resource-poor countries. It is estimated that between 60% and 90% of infections in most Asian countries go undiagnosed (unpublished data, 2012) and, unless they cause an epidemic, are promptly forgotten. It is these pathogens, which under the right ecological circumstances will cause SARS-like epidemics, that threaten economic and public health security.
The trends of economic and urban growth and globalisation are projected to continue for the indefinite future, with the Asia–Pacific region leading the way.9,10 Thus, it is likely that most newly emergent pathogens will be zoonotic and will originate in Asia.11 The world is now highly vulnerable to emergent epidemic infectious diseases that can threaten global economic security and public health. Although programs to prevent this threat are being developed, it will take years before they are effectively implemented in those countries where they are most needed.
Competing interests
No relevant disclosures.
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Provenance: Commissioned; externally peer reviewed.