Epidemiology is the study of the incidence and distribution of diseases. This definition provides an important distinction between epidemiologists and other researchers who study infectious diseases. Where another kind of disease biologist might be concerned with how a pathogen infects its host or how it works once it’s inside, an epidemiologist studies that pathogen at the population and landscape level: how the genetic diversity of a pathogen changes over time, how it spreads across the world, whether certain populations are more susceptible to it, and where it started.
Understanding how a disease works once it has infected its host is critical to fighting that disease, but epidemiology provides an overhead view of the entire phenomenon, creating space for high-level strategy in the fight against it and even potentially enabling researchers to spot outbreaks before they reach epidemic or pandemic status. Thermo Fisher Scientific tools, technologies and reagents provide the edge that researchers need for their epidemiological studies.
Tracking the Spread of a Virus
Epidemiologists have had their hands full with the SARS-CoV-2 pandemic. This virus has rapidly spread across the world in the past year and imposed an enormous toll of human suffering. At local levels, epidemiological research can help track the spread of the virus, which provides focused, direct information that can inform public health efforts. This is the kind of information that can illuminate whether city-wide lockdowns, quarantines of symptomatic individuals and other measures, alone or in combination, are the right approach for stopping the virus’s spread. For example, Yuan et al.used Big Dye Direct and Sanger sequencing to track a handful of new cases in Hunan province, China, to a single asymptomatic carrier. This finding made clear that restricting the movement only of symptomatic people would not be an effective public health strategy, since asymptomatic people were demonstrably spreading the infection.1
Finding New Strains
SARS-CoV-2 has also evolved, with new strains being identified in the UK, South Africa, Brazil, and other countries in recent months. Because it makes no assumptions about the mutational landscape, identifying these variants involves sequencing the entire genome of the virus, and for that the Ion AmpliSeq™ SARS-CoV-2 research panel is ideal. For example, Bartolini et al. identified a new strain that was circulating in Lazio, Italy.2 When and where a new strain arises are important data that epidemiologists need so that they can alert areas where the new strain has not yet become established. This level of preparation can be the difference between a sudden crisis and a well-managed pandemic response.
Wastewater Surveillance
One of the most important innovations in epidemiological research related to SARS-CoV-2 is the widespread use of wastewater surveillance. Infected people shed virus particles in their feces3 and the overall concentration of these particles provides a window into population-level infection rates and viral loads.4 Canadian cities have used qPCR and Sanger sequencing to track SARS-CoV-2 presence in sewage. This approach provides an ideal way to gather data on the prevalence of SARS-CoV-2 variants in a population, and may lead to the discovery of new variants.5
Epidemiology and Drug Development
Epidemiological data is crucial for drug and vaccine research. By discovering and tracking new variants as they emerge, epidemiological data can potentially illuminate which parts of a virus’s genome mutate rapidly and thus may make poor targets for vaccines and drugs. For example, Plante et al. developed an in vitro system for characterizing the fitness of SARS-CoV-2 variants. Using a combination of PCR (to generate mutant strains) and Sanger sequencing of virus in co-infected cultures to compare the relative fitness of different strains, they showed that a spike D614G mutation conferred enhanced fitness in culture.6 It therefore is important to test therapeutic candidates against this strain, to inform drug and vaccine development.
Epidemiology is both a natural partner to direct research into disease-causing organisms and a critical part of fighting diseases once they spread to large areas. By studying diseases at the population level, epidemiologists gather critical information necessary to guide public health measures and get ahead of the spread of virus as it begins to affect new areas. With our robust and expansive assortment of Sanger sequencing, fragment analysis, qPCR, and targeted sequencing tools and reagents, Thermo Fisher Scientific is an ideal partner for researchers seeking to get ahead of the SARS-CoV-2 global crisis and gain insight into how its future will unfold.
Learn more about our real-time PCR, Sanger sequencing and fragment analysis, and targeted sequencing solutions for epidemiological surveillance.
For research use only. Not for use in diagnostic procedures.
References
1. Yuan, Y., He, J., Gong, L., et al. (2020). Molecular epidemiology of SARS-CoV-2 clusters caused by asymptomatic cases in Anhui Province, China. BMC Infect. Dis. 20(1):930.
2. Bartolini, B., Rueca, M., Gruber, C.E.M., et al. (2020). The newly introduced SARS-CoV-2 variant A222V is rapidly spreading in Lazio region, Italy. medRxiv:2020.11.28.20237016.
3. Chen, Y., Chen, L., Deng, Q., et al. (2020). The presence of SARS-CoV-2 RNA in the feces of COVID-19 patients. J. Med. Virol. 92(7):833–840.
4. Rimoldi, S.G., Stefani, F., Gigantiello, A., et al. (2020). Presence and infectivity of SARS-CoV-2 virus in wastewaters and rivers. Sci. Total Environ. 744:140911.
5. Martin, J., Klapsa, D., Wilton, T., et al. (2020). Tracking SARS-CoV-2 in Sewage: Evidence of Changes in Virus Variant Predominance during COVID-19 Pandemic. Viruses 12(10).
6. Plante, J.A., Liu, Y., Liu, J., et al. (2020). Spike mutation D614G alters SARS-CoV-2 fitness. Nature:1–6.
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