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Global Health Econ Sustain Implication of close contact

number of direct interactions among individuals (Murray, birth rate required in these models is significantly higher
2002). However, the key elements facilitating the rapid than the actual birth rate in the respective regions. For
spread of COVID-19 were the variability of possible example, Chile has a birth rate of approximately 12 births
symptoms and the pre-symptomatic infectivity (He et al., per year per 1000 people. On the other hand, the stationary
2020). Consequently, an undetected number of infective daily case rate was around 1700 cases per day in the Region
individuals may have been amplifying the epidemic Metropolitana (the most populated region, where Santiago
within their community and even potentially exporting de Chile is located) between August and November 2020,
the infection to other regions without realizing that they which equates to an estimated 110 cases per year per
were ill. For symptomatic individuals, COVID-19 exhibits 1000 people, far surpassing the rate of new susceptible
higher contagiousness around the time of symptom onset individuals needed to maintain a stable epidemic.
(around 5 days after acquiring the infection); however, the Other authors have incorporated time-dependent
infectivity gradually decreases and reaches zero within variables into their models, which were adjusted to
an average of 10–15 days (He et al., 2020; Rhee et al., reproduce clinical data (Zhao & Chen, 2020; Bagal et al.,
2021). Therefore, promptly identifying any asymptomatic 2020; El Fatini et al., 2021). These models account for
spreaders among the close contacts of symptomatic various stages of epidemics and consider variations in the
individuals can significantly mitigate the impact of the strength of quarantine policy. As a result, they predicted
epidemic (Kwon et al., 2020). Initial analysis suggested that the epidemic would subside within a couple of months
that successfully tracing 70% of contacts (approximately and not exhibit an equilibrium evolution. However, Choi
36 people in the United Kingdom) could be an effective & Ki (2020) were able to achieve an equilibrium behavior
strategy for containing an outbreak (Anderson et al., 2020). modeling the evolution of the epidemic in South Korea by

South Korea was one of the first countries outside adjusting the model parameters in five different intervals
China to experience the impact of the COVID-19 epidemic and selecting a value close to 1 for the basic reproductive
(Shim et al., 2020). To control the spread of the disease, rate at equilibrium.
various non-pharmaceutical mitigation measures were We acknowledge that certain parameters in epidemic
implemented, including some controversial approaches, models are time-dependent due to variations in people’s
such as the extensive use of information technology to activity during different public health policies. However,
trace contacts (Park et al., 2020). These measures make we believe that the prolonged stationary behavior (lasting
South Korea an excellent case for analysis. In this respect, more than 100 days in South Korea) cannot be solely
several different models have been considered to describe attributed to an exact compensation between epidemic
the evolution of the disease in different countries, including evolution and people’s interactions. Moreover, data
South Korea, with the aim of predicting the timing and analysis indicates the existence of three different stationary
magnitude of the peak of the epidemic (Adam, 2020). stages for daily COVID-19 cases in South Korea. The
These models include individual-based network models analysis suggests the presence of a mechanism that leads
(Son & Team, 2020; Ferguson et al., 2020) and simpler to equilibrium through competition between different
compartmental models (CMs) (Wang et al., 2020; Reis processes. In this respect, we consider that this epidemic
et al., 2020). behavior is a result of a balance between the spread of
Compartmental models are utilized by assuming a fast- disease and the government policies implemented to
mixed and homogeneous population where all individuals control it, particularly the intensive search for cases among
have the potential to come into contact with one another. close contacts of newly infected individuals. In this regard,
In this context, South Korea or New York City serves as South Korea, once again, provides an excellent case study
excellent examples of applying a CM. However, while due to its strong campaign of mass testing and contact
many studies have employed CMs to analyze the spread tracing of infected individuals (Park et al., 2020; Kim
of COVID-19 in South Korea (Kim et al., 2020; Magal et al., 2020).
& Webb, 2020), these models fail to accurately capture The outbreak of coronavirus has not only triggered
the long stationary phase observed between April and a global crisis but has also introduced an epidemic with
August 2020, preceding the second wave of the pandemic new characteristics that have made it challenging to halt
(Worldometers.info, 2021). Similar behavior has been its spread. First, there is a wide spectrum in the disease
observed in diverse regions (cities or countries) such as severity, ranging from asymptomatic individuals to those
New York City or Chile. Some researchers have incorporated resulting in fatalities. Second, individuals infected with
birth and death processes into their models to account for the virus become contagious before the appearance of
this stationary phase (Wang et al., 2020). However, the symptoms or even without ever exhibiting any symptoms.

Volume 1 Issue 1 (2023) 2 https://doi.org/10.36922/ghes.0873