Policy ForumEpidemiology

Infectious Diseases: Preparing for the Future

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Science  08 Sep 2006:
Vol. 313, Issue 5792, pp. 1392-1393
DOI: 10.1126/science.1129134

Infectious diseases account for a quarter of all human mortality and a similar fraction of morbidity (1). Infectious diseases of crops and livestock cost the global economy uncounted billions of euros every year. On top of this, sudden epidemics of infectious diseases can deliver humanitarian and economic shocks on a scale difficult to absorb. According to the World Bank, the 2003 severe acute respiratory syndrome (SARS) epidemic, which killed fewer then 1000 people, was responsible for an estimated 2% fall in gross domestic product (GDP) across East Asia, and an influenza pandemic could kill millions of people and cost €700 billion (U.S. $900 billion) globally in a single year (2). In recent years, there have been numerous outbreaks of livestock and crop diseases costing individual countries billions of euros, for example, foot-and-mouth disease (FMD) in Taiwan and the United Kingdom; bovine spongiform encephalopathy (BSE) in the United Kingdom; classical swine fever (CSF) in the Netherlands; soybean rust in Brazil; Southern corn leaf blight in the United States; and, most recently, avian influenza in Egypt. The United Nations Millennium Development Goals, as well as having explicit targets for reducing the burden of human diseases (particularly HIV/AIDS, tuberculosis, and malaria), also have targets for reducing poverty and hunger, but these are compromised by crop and livestock diseases. In most developing regions, where the impacts of infectious disease are greatest, there is now little hope of meeting any of the Millennium Development Goals by 2015 (3).

Governments and international agencies need a vision of how threats such as infectious diseases are likely to evolve in the future so that they can identify effective science and technology strategies to help meet the challenge. Foresight programs, largely originating in Japan and the USA, were put in place precisely to do this. The U.K.'s Foresight program established a series of cross-disciplinary projects to study selected topics in depth, incorporating two key principles (4). First, the work has to be based on peer-reviewed science presented in a way that is accessible to nonscientists, and second, decision-makers and government must be engaged from the outset in setting the direction and broad approach of each project.

The latest Foresight project to report (5) assessed the projected risks from infectious diseases of humans, animals, and plants over 10- and 25-year horizons. The project focused specifically on detection, identification, and monitoring of disease, aspects widely perceived as neglected and where the development and deployment of new technologies and systems could have major impacts. Earlier disease detection would buy time to allocate resources and, by contrast to current reactive approaches, enable proactive disease management.

The project compared three geographical regions: the United Kingdom (as an example of a developed country), China (a rapidly emerging economy), and sub-Saharan Africa (a developing region). In total, over 300 experts in some 30 countries were consulted by a variety of methods, including Delphi studies (which use formal methods to generate forecasts from groups of experts), expert reviews, workshops, mathematical modeling, and commissioned research.

Eight categories of infectious diseases of the future were identified for which improved detection systems would make a difference over the next 10 to 25 years.

(i) New diseases, such as SARS and BSE, and novel variants, such as H5N1 subtype influenza A, are anticipated to continue emerging. (ii) Infections are becoming resistant to treatment, including antibiotic-resistant bacterial infections, such as tuberculosis and methicillin-resistant Staphylococcus aureus (MRSA). (iii) Zoonoses, i.e., infections transferring to humans from animals, are associated with livestock, pets, and, in many cases, with wildlife, e.g., SARS, avian influenza, plague, Lyme disease, and anthrax. This category includes food-borne infections such as Escherichia coli O157 or Salmonella. Other categories are (iv) HIV/AIDS, tuberculosis, and malaria, the “Big Three” tropical diseases covered by U.N. Millennium Development Goal 6; (v) epidemic plant diseases, such as cassava mosaic virus and banana blight, currently of concern in East Africa; (vi) acute respiratory infections, a category that covers pandemic influenza and a variety of other viral and bacterial infections; (vii) sexually transmitted infections (STIs), including but not limited to HIV/AIDS, which are increasing in incidence in many parts of the world; and (viii) animal diseases, such as FMD, CSF, and Newcastle disease, which remain among the most important barriers to international trade in livestock and livestock products.

Records of mobile phone location could be useful for contact tracing during infectious disease outbreaks. CREDIT: PHOTOS.COM

The categories are not mutually exclusive and are not intended to be exhaustive, but the list does capture the priority concerns identified by the project. These differed for different regions, e.g., African experts were less immediately worried about new, emerging diseases, and Chinese experts highlighted health care-associated infections as an increasing problem. Overall, it is clear that the infectious disease threat is diverse and dynamic, including “out-of-the-blue” events akin to the emergence of BSE in the United Kingdom in the 1980s, which implies a need for detection systems that are flexible and adaptable in the face of change.

Among the most important factors expected to influence future changes in infectious disease risks were travel, migration, and trade, which promote the spread of infections into new populations. Particularly worrisome is the trade in exotic species, whether as livestock, pets, crops, garden plants, or food. Changes in land use and agricultural practices, as well as increasing urbanization, were all expected to contribute to changes in infectious disease patterns. Although climate change was a concern, modeling studies suggested that its effect on infectious diseases will be relatively minor over the next 10 to 25 years, becoming potentially more serious in the longer term, both directly, e.g., through changing the distribution of disease vectors and indirectly, e.g., by changing patterns of land use and agriculture. Poor governance and the loss of capacity to recognize and respond to infectious disease problems is a major issue for sub-Saharan Africa in particular. The report also anticipated that, despite the alarming spread of antibiotic resistance, widespread overuse and misuse of antibiotics and other drugs would continue, further exacerbating drug resistance problems. Taken together, these drivers of changing infectious disease risk have complex and interrelated effects, making the prediction of future risk extremely uncertain and again underlining the need for flexible detection systems.

A wide range of technological advances, from remote sensing to nanotechnology, were reviewed and ultimately four were selected for detailed consideration (5). Novel information technologies for the capture, analysis, and modeling of data are already being developed. These will allow data to be collected electronically from hand-held devices or remote sensors and analyzed and modeled in real time. Genomics and postgenomics approaches will allow the rapid characterization of pathogens. Mass screening of people, animals, and plants in transit should become feasible through noninvasive detection systems for volatile organic chemicals or atypical electromagnetic profiles. Portable devices will become available for diagnosing infections in individual patients, animals, or plants, satisfying a growing demand for cheap, quick, easy-to-use, over-the-counter products, perhaps resembling today's home pregnancy test kits. Some of these technologies will be generic, such as “lab-on-a-chip” screening for a range of infectious agents, nonspecific diagnostics based on detecting activated immune responses, or simple tests to differentiate between viral and bacterial infections to aid the appropriate prescription of antibiotics.

Better disease detection capability is vital but will present challenges as well as opportunities. New technologies must be embedded within functional national or international surveillance systems. In practice, it is not clear whether or how government agencies would gain access to valuable data obtained through the widespread use of self-administered tests. Other kinds of information, e.g., records from mobile phones or traffic cameras to follow movements, are potentially valuable for disease-control purposes, particularly in outbreak situations, but the public might not accept their use for this purpose. There is always the danger that disease data could be used to discriminate against individuals without providing any benefit or compensation. Similarly, technologies deployed by developed countries could disadvantage developing countries by restricting travel and trade on the basis of the presence or even the suspicion of an infectious disease. Finally, everywhere in the world, better disease data might cause public alarm and raise expectations of effective action, whether or not this is realistic. Surveillance needs to be linked operationally to an appropriate response. For example, the Global Plan to Stop TB relies on the combination of case detection and directly observed therapy (DOTS) (6), and plans to combat influenza involve surveillance, drug delivery, and vaccine production (7).

The Foresight project highlighted the importance of fostering interdisciplinary approaches to infectious disease research that transcend traditional intellectual boundaries, such as those between medicine and veterinary medicine or among virology, bacteriology, mycology, and parasitology. A better understanding of patterns of infectious disease also needs input from disciplines as diverse as anthropology, economics, and climatology. Quantifying these relations and understanding their dynamics require inputs from statistics and mathematics. Health systems research is needed to understand how new technologies can be used most effectively and must include consideration of the needs, expectations, capabilities, and sensitivities of end users and other stakeholders.

The Foresight project also highlighted a number of key choices for policy-makers. Among the most important of these was that more extensive international coordination should be sought by building on the work of the World Health Organization, the World Organization for Animal Health, the Food and Agriculture Organization, and other agencies. For this to be effective it is essential that data and biological material can be rapidly collected and openly shared. Recent success in combating SARS illustrates what can be achieved (8). Currently, the extreme disparity in detection and disease management capabilities between nations, reflecting massive inequalities in wealth, often exacerbated by poor governance, seriously hinders our ability to tackle infectious disease problems quickly.

In the 1940s, the U.S. government created a national rapid response capability, now the Centers for Disease Control and Prevention, in response to malaria originating from Africa. Sixty years later, Africa and other regions still do not have equivalent capabilities of their own, or the infrastructure, skills, and training base to support them. The Foresight report advocates the benefits of a system of regional reference and coordination centers (RRCCs). These would form a network of high-quality laboratories linked to one another, to existing facilities, and to appropriate partners in developed countries. Collectively, the network would have the physical and human resources to support infectious disease detection, identification, and monitoring and the development of suitable technologies and appropriate training programs. The network would aim to cover a range of diseases of humans, animals, and plants, exploiting the commonalities across different disease problems and so being more cost-efficient than traditional “one-disease-at-a-time” initiatives. It is ever more apparent that the benefits of such a facility would extend not just nationally or regionally, but globally; surveillance for infectious diseases has become a collective responsibility and requires a collective investment. The recent statement from the G8 summit in Russia, which calls for “tangible progress” on international disease surveillance (9), will, we hope, encourage the international community to make that investment.

References and Notes

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