Emerging infectious diseases—diseases that are recognized in the human host for the first time—have had significant impact on human health and global stability. Moreover, the potential emergence of pandemic viruses to which the human population is highly susceptible continues to be a concern because of the catastrophic consequences of these events. Some recent examples include the human immunodeficiency virus (HIV), severe acute respiratory syndrome-associated coronavirus (SARS-CoV), and the 2009 pandemic H1N1 influenza virus. Although we know now that most emerging human diseases have an origin in animals (also known as zoonotic infections), their emergence in the human population has been so far unpredictable. Prior to the emergence of a novel pathogen in the human population, it circulates in its animal reservoir before it could spread to other animals impacting animal health and trade. Outbreaks of novel zoonotic infections signal a spillover event into humans where as human-to-human transmission of these pathogens would suggest the possibility of large-scale spread of these emerging infections. It is the responsibility of governments and public health authorities to detect the emergence of novel pathogens before they appear, as well as to effectively prevent and control the spread of these diseases in the animal and human population.
In 2003, the Severe Acute Respiratory Syndrome-associated coronavirus (SARS-CoV) emerged from bats in China and spread into humans. Human-to-human transmission of SARS mainly happened between close contacts and within hospitals. But it was the international human movement through air travel, which facilitated spread of SARS worldwide. During this global epidemic, more than 8,000 probable cases of SARS and 774 deaths were reported to the World Health Organization. During the same time, the world confronted the possibility of another pandemic with the unprecedented emergence a highly pathogenic H5N1 avian influenza virus in China from free-ranging wild birds, especially waterfowl. Outbreaks in wild bird and subsequent transmission to domestic poultry worldwide resulted in the transmission of this highly pathogenic avian influenza (HPAI) H5N1 virus to humans exposed to infected poultry in several countries in Asia, Africa, and the Middle East. On the other hand, the inevitable emergence of new pandemic and seasonal strains of human influenza viruses has resulted in outbreaks, epidemics, and three pandemics. The most recent influenza pandemic was caused by a novel H1N1 influenza A virus, which emerged in Mexico. This novel influenza A virus was able to sustain human-to-human transmission more effectively than SARS thereby causing outbreaks in more than 214 countries and territories. Moreover, surveillance data from past influenza seasons in the United States show that descendants of this virus continue to circulate and cause disease.
Although we know now a lot more about the underlying factors of disease emergence than in the past, the exact processes that allow unknown pathogens to emerge or known pathogens to ‘re-emerge’ in the human population remain elusive. Our understanding of how pathogen biology as well as ecological, environmental, and host factors contribute to the spillover of animal diseases in humans has lead to improvements in the control of zoonotic disease outbreaks and epidemics in humans. On the other hand, the health and economic effects associated with pandemic events reminds us of the threat of emerging diseases.
A greater awareness about the threat of novel pandemic virus able to sustain human-to-human transmission has lead to new research agendas aimed at identifying the molecular markers of pathogenicity and transmissibility of avian influenza and pandemic viruses. At the global level, the World Health Organization revised the International Health Regulations with the goal of improving the preparedness and response capacity of countries to future pandemics. Nevertheless, the detection for the first time of a novel coronavirus in Saudi Arabia in 2012 causing severe respiratory disease like SARS provides further evidence of the persistent threat of emerging diseases. Columbia University investigators and collaborators are currently involved in research on the animal reservoir of this novel coronavirus, known as the Middle East Respiratory Syndrome coronavirus (MERS-CoV). So far, the evidence generated suggests that bats may be the source of MERS-CoV infections in the Arabian Peninsula, but the mode of transmission to humans is still unknown. Therefore, there is a critical need of countermeasures such as, surveillance, drugs, and vaccines. Additionally, the strategic and efficient use of resources to manage the risk and mitigate the impact of these novel diseases is necessary.
The public health focus group of CMSR is working on a collaborative project involving researchers from the School of Engineering and the Mailman School of Public Health (see below) aimed at adapting concepts, techniques, and tools from systems engineering to improve the modeling, design, monitoring, regulation and management of public health systems to minimize the systemic risk due to emerging infectious diseases, in particular pandemic viruses. There is a clear need for prediction models that can help us identify where the potential infectious disease risks are and to recognize early signs of systemic failure as well as to develop methods for managing systemic risk, including secondary consequences of the public health response to the spread of disease, more effectively. The ultimate goal is to implement these models in software in order to provide tools that can be used by public health practioners and policy makers for the better monitoring and management of systemic risk.
In other related efforts, our faculty work on research projects that enhance system readiness for mega-disasters, foster community preparedness and engagement, understand population vulnerability, and explore strategies to improve disaster recovery.