To date, the COVID-19 epidemic is still in a phase of rapid dispersion worldwide, and this epidemic represents a clear and ongoing global health threat. It is currently uncertain whether it is possible to contain the continuing epidemic within China [
25]. In the early stage of a SARS-CoV-2 outbreak, the medical conditions are not ideal, and no effective measures have been taken. The number of infected people increases exponentially, so it is particularly critical to control the value of
β. In our model, the
β of South Korea is 0.359, which is the lowest among the three countries, followed by Italy, whose
β is 0.4. The
β of both South Korea and Italy is lower than that of China. In these three countries, the trend of
R0 was consistent with
β. Thus, reducing the exposure rate of
β could significantly reduce the reproduction number. Next, we estimated an
R0 of 6.66 in Wuhan, which represents a relatively higher value than those computed so far (as of Mar 01, 2020). In several other mathematical models that have been devised and released to date,
R0 varies from 1.30 to 6.47 (Additional files
1,
2: Table S1) [
26‐
30]. By comparing the methodologies of the various investigations, these different reproduction numbers reflect the dynamics of transmission, and the cases of COVID-19 fluctuate and vary over time. In our models, we used these data (Jan 15, 2020–Mar 01, 2020) to estimate a relatively accurate
R0, which was relatively reliable in our models.
We further took hospital isolation and SARS-CoV-2 drugs and vaccines into account in our models. With other parameters unchanged, the greater the
α for the isolation rate in the hospital, the later the peak is reached, the smaller the peak size, and the more effective it is to prevent the spread of the disease. The hospital pathway should sufficiently isolate SARS-CoV-2-infected patients from other patients to decrease infection, and more concern should be given about protecting doctors and nurses [
31]. For the penetration of vaccines and drugs, the greater the parameter theta, the earlier the peak would appear, the smaller the peak would be, and the lower the final total number of infections would be. However, scientists have still not found effective medications and vaccines for SARS-CoV-2 [
32]. Finally, our simulations have shown that the containment outcome depends highly on the effectiveness of the intense control effort now underway in China. Reducing the exposure rate of
β and increasing the isolation rate of
α can significantly reduce the number of infected people. The government should continue to tightly monitor the epidemic situation and must take immediate measures against it, and this includes immediate isolation of newly infected people and closures of cities with severe outbreaks, in case there are unexpected outbreaks in the eradication process. Regional transmission is the root of the spread of COVID-19. Local governments must have the responsibility to set a deadline for the final eradication, and the SARS-CoV-2 epidemic in the world revealed that all the countries still need to strengthen the establishment of a rapid outbreak response strategy and health policies. Finally, there were some limitations in our SIR or SEIR models of SARS-CoV-2, such as we only used the average latency value during the latent period. We recognized that some patients with COVID-19 have a longer latent period, while others have a shorter latent period of only 4 days, which affects the basic reproduction number (
R0) [
33]. In addition, we need to consider “superspreading events and superspreaders”, which tend to occur at large gatherings with close contact [
34], transmit infection to a larger number of individuals than is typical by one individual [
35], and affect
R0. For example, a man who later tested positive for COVID-19 visited several clubs in Seoul and infected 170 new individuals after South Korea relaxed social distancing rules in May. Moreover, the differences in case definitions and reporting measures, city closures and leave policies, and viral testing would likely affect the basic reproduction number and the secondary attack rate (SAR) [
34,
36]. It is important that the Italian government implemented extraordinary measures to limit viral transmission in March 2020 and minimized the likelihood that people were infected [
37]. Therefore, all those countries that had beaten back the virus to low levels need to be especially vigilant for superspreaders and superspreading events.