Systems Biology-Based Platforms to Accelerate Research of Emerging Infectious Diseases

Oh, Soo-Jin; Choi, Young-Ki; Shin, Ok Sarah

There are several factors contributing to the emergence of new pathogens: microbial adaptation and genomic change, increased frequency of international travel and commerce, and climate change. 17 Given that microbial adaptation is driven by the evolution of microbes to survive in diverse environments, microbes have evolved to change their genomes. RNA viruses carry RNA as their genetic material and can quickly adapt to and exploit different hosts because of the high error rates of the viral enzymes (RNA-dependent RNA polymerases) during their replication. 18 The segmented nature and faulty replication mechanisms of Orthomyxoviruses promote genetic variability and frequent re-assortment events, resulting in genetically diverse and novel genomic constellations in infected hosts. 19 As an example, hemagglutinin surface proteins of the influenza A virus undergo antigenic drift and shift, acquiring new infectivity and evading recognition by the immune system. 20 Another important consequence of the unstable genomic make-up of RNA viruses is the potential for interspecies transmission between animal hosts and humans. Accordingly, the recent emergence of avian influenza viruses could be devastating in an immunologically naïve population and pose a serious threat to public health. 21 Another major factor responsible for EIDs is an increased incidence of international travel and commerce. 22, 23 The frequent use of air travel has enabled increased globalization, and international tourism has expanded 1.5 times in the last decade. Many travelers can be infected by and become carriers of EID pathogens without their knowledge. A viral incubation period can frequently last more than 2 weeks; thus, it is impossible to successfully monitor travelers with EIDs at an early stage of infection. 24 Surveillance of travelers with respiratory illness is especially difficult, because respiratory viruses can propagate easily and cause outbreaks in non-endemic disease areas. For example, in 2015, South Korea experienced a MERS outbreak, which was initiated by a man who had traveled from Bahrain, which is located in the Middle East. 25 Despite South Korea being a non-endemic area for MERS, 186 cases were reportedly infected with MERS-CoV during the 2015 outbreak, and this number was the highest among MERS non-endemic areas. 26 Lastly, climate change can contribute to ecological changes and, thus, contribute to the emergence of EIDs. Over the last 10 years, the temperature of the earth has increased by approximately 0.4°C, and this global warming has contributed to climate change throughout the world. A warmer climate can provide a more favorable environment for the survival and completion of the vector life cycle. 27 In particular, the mosquito population has been widely established across Europe, as well as tropical regions, such as Africa and South Asia. 28 As an example, prior to 1970, only nine countries had experienced dengue fever, which is transmitted by mosquitoes and occurs mostly in tropical regions. However, today, cases of DENV-associated disease can be found in more than 125 countries. 29 Moreover, climate change is frequently invoked as a primary cause of expansions in incidences of tick-borne diseases, particularly Lyme disease. 30 A wide distribution of tick vectors increased the prevalence of tick-borne pathogens, given that rising temperatures accelerate the cycle of development, the production of eggs, and the density and distribution of the t