Osong Public Health and Research Perspectives

Sunmi Lee

5 Articles

The Characteristics of Middle Eastern Respiratory Syndrome Coronavirus Transmission Dynamics in South Korea: Yunhwan Kim, Sunmi Lee, Chaeshin Chu, Seoyun Choe, Saeme Hong, Youngseo Shin; Osong Public Health Res Perspect. 2016;7(1):49-55. Published online February 28, 2016; DOI: https://doi.org/10.1016/j.phrp.2016.01.001

Abstract PDF: Objectives
The outbreak of Middle Eastern respiratory syndrome coronavirus (MERS-CoV) was one of the major events in South Korea in 2015. In particular, this study pays attention to formulating a mathematical model for MERS transmission dynamics and estimating transmission rates.
Methods
Incidence data of MERS-CoV from the government authority was analyzed for the first aim and a mathematical model was built and analyzed for the second aim of the study. A mathematical model for MERS-CoV transmission dynamics is used to estimate the transmission rates in two periods due to the implementation of intensive interventions.
Results
Using the estimates of the transmission rates, the basic reproduction number was estimated in two periods. Due to the superspreader, the basic reproduction number was very large in the first period; however, the basic reproduction number of the second period has reduced significantly after intensive interventions.
Conclusion
It turned out to be the intensive isolation and quarantine interventions that were the most critical factors that prevented the spread of the MERS outbreak. The results are expected to be useful to devise more efficient intervention strategies in the future.

Assessment of Intensive Vaccination and Antiviral Treatment in 2009 Influenza Pandemic in Korea: Chaeshin Chu, Sunmi Lee; Osong Public Health Res Perspect. 2015;6(1):47-51. Published online February 28, 2015; DOI: https://doi.org/10.1016/j.phrp.2014.11.007

Abstract PDF: Objectives
We characterized and assessed public health measures, including intensive vaccination and antiviral treatment, implemented during the 2009 influenza pandemic in the Republic of Korea.
Methods
A mathematical model for the 2009 influenza pandemic is formulated. The transmission rate, the vaccination rate, the antiviral treatment rate, and the hospitalized rate are estimated using the least-squares method for the 2009 data of the incidence curves of the infected, vaccinated, treated, and hospitalized.
Results
The cumulative number of infected cases has reduced significantly following the implementation of the intensive vaccination and antiviral treatment. In particular, the intensive vaccination was the most critical factor that prevented severe outbreak.
Conclusion
We have found that the total infected proportion would increase by approximately six times under the half of vaccination rates.

Assessment of the Intensive Countermeasures in the 2009 Pandemic Influenza in Korea: Jin Hyuk Choi, Yunhwan Kim, Seoyun Choe, Sunmi Lee; Osong Public Health Res Perspect. 2014;5(2):101-107. Published online April 30, 2014; DOI: https://doi.org/10.1016/j.phrp.2014.03.003

Abstract PDF: Objectives
It is critical to implement effective multiple countermeasures to mitigate or retain the spread of pandemic influenza. We propose a mathematical pandemic influenza model to assess the effectiveness of multiple countermeasures implemented in 2009.
Methods
Age-specific parameters, including the transmission rate, the proportion of asymptomatic individuals, the vaccination rate, the social distancing rate, and the antiviral treatment rate are estimated using the least-square method calibrated to the incidence data.
Results
The multiple interventions (intensive vaccination, social distancing, antivrial treatment) were successfully implemented resulting in the dramatic reduction in the total number of incidence.
Conclusion
The model output is sensitive to age-specific parameters and this leads to the fact that a more elaborate age group model should be developed and extensive further studies must be followed.

What Does a Mathematical Model Tell About the Impact of Reinfection in Korean Tuberculosis Infection?: Sara Kim, Seoyun Choe, Junseong Kim, Sanga Nam, Yeon Shin, Sunmi Lee; Osong Public Health Res Perspect. 2014;5(1):40-45. Published online February 28, 2014; DOI: https://doi.org/10.1016/j.phrp.2014.01.002

Abstract PDF: Objectives
According to the Korea Centers for Disease Control and Prevention, new active tuberculosis (TB) cases have increased since 2001. Some key factors explain and characterize the transmission dynamics of Korean TB infection, such as a higher ratio of latent individuals and a new reporting system implemented in 2001, among others.
Methods
We propose a mathematical TB model that includes exogenous reinfection to gain a better understanding of the recent trend for TB incidence. We divide the simulation time window into two periods, 1970–2000 and 2001–2012, according to the implementation date of a new TB detection system.
Results
Two sets of parameters, including the transmission rate, the latent period, the recovery rate, and the proportion of exogenous reinfection, are estimated using the least-squares method and calibrated to data on the incidence of active TB.
Conclusion
Among some key parameters in the model, the case finding effort turned out to be the most significant impacting component on the reduction in the active TB cases.

Role of Active and Inactive Cytotoxic Immune Response in Human Immunodeficiency Virus Dynamics: Hernan Dario Toro Zapata, Angelica Graciela Caicedo Casso, Derdei Bichara, Sunmi Lee; Osong Public Health Res Perspect. 2014;5(1):3-8. Published online February 28, 2014; DOI: https://doi.org/10.1016/j.phrp.2014.01.001

Abstract PDF: Objectives
Mathematical models can be helpful to understand the complex dynamics of human immunodeficiency virus infection within a host. Most of work has studied the interactions of host responses and virus in the presence of active cytotoxic immune cells, which decay to zero when there is no virus. However, recent research highlights that cytotoxic immune cells can be inactive but never be depleted.
Methods
We propose a mathematical model to investigate the human immunodeficiency virus dynamics in the presence of both active and inactive cytotoxic immune cells within a host. We explore the impact of the immune responses on the dynamics of human immunodeficiency virus infection under different disease stages.
Results
Standard mathematical and numerical analyses are presented for this new model. Specifically, the basic reproduction number is computed and local and global stability analyses are discussed.
Conclusion
Our results can give helpful insights when designing more effective drug schedules in the presence of active and inactive immune responses.

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