▲Prof. Ki Moran at National Cancer Center Korea
Lee Hee Hoon
Professor Ki Moran released a prediction of the future COVID-19 spread in Daegu and Gyeongsangbuk-do Province through mathematical modeling on March 12th. Mathematical modeling for infectious diseases is to predict the spread by utilizing differential equations and so on.
According to Professor Ki Moran's analysis of the confirmed number of cases from Feb. 18th to March 4th, when the first patient in Daegu(the 31st patient) was identified, the reproductive number was higher than 3. If the reproductive number is 1, it means one COVID-19 patient infects one person, and the trend of COVID-19 remains. Only when the reproductive number is less than 1, will the number of confirmed cases decrease. The reproductive number can be lowered through social distancing.
Professor Ki has prepared five scenarios, of which 'Scenario 5' fits the current situation. According to the scenario, April 10th will be the day when the number of confirmed cases in Daegu and Gyeongsangbuk-do Province is less than 10 per day. And May 1st is the day the number of confirmed cases will be less than one case a day. The total number of patients will be 10,249. As of midnight on March 19th, the confirmed cases in Daegu and Gyeongsangbuk-do Province are 7,431. Therefore, it is predicted that 2,800 more will be infected. The basic premise of this scenario is that there is no COVID-19 inflow from other areas apart from Daegu and Gyeongsangbuk-do Province.
- Is the current situation going like Scenario 5?
"The increase rate of the confirmed cases has decreased faster. Under the current situation, the total number of patients could be between 8,000 and 9000. This is the result of people working harder at social distancing."
- Group infections continue to occur in the Seoul area.
"I haven't received Incheon data yet, so I analyzed it with the data only from Seoul and Gyeonggi-do Province. Unlike Daegu and Gyeongsangbuk-do Province, I did mathematical modeling on the assumption that there are the external inflows in Seoul and Gyeonggi areas, and the reproductive number is 0.8."
- If so, doesn't it mean the spread of COVID-19 will decrease in the Seoul metropolitan area as well?
"It doesn't decrease much. The reproductive number must fall below 0.5 for COVID-19 to be fully terminated. (On Feb. 12th, when we did the first interview), the total number of confirmed cases was only 28, and the reproductive number was 0.5. Since 0.8 is close to 1, the trend continues. It won't end completely."
- Does it mean we can't terminate COVID-19 for good?
"That's the scenario we're worrying about because if the reproductive number stays between 0.8 and 1, COVID-19 becomes indigenous. It's called endemic, which means there's always a certain amount of patients."
- Then, will COVID-19 become like the flu or a cold?
"The flu is a seasonal epidemic that comes back in time. But a cold is endemic that occurs all year round. Of the six types of coronavirus, excluding SARS and MERS, 4 types remain like a cold. COVID-19 has a high fatality rate for the elderly as it is easy to transmit. While the elderly don't die from a cold or the flu in nursing homes, many people die when COVID-19 goes around. Also, unlike the flu, there is no cure or vaccine for COVID-19."
- No matter what we do, we have to prevent COVID-19 from being endemic, right?
"Can we wipe it out completely? I think it will be very difficult if the whole world doesn't try very hard. China, which has seen a significant drop in the number of confirmed cases, is also not able to relax. Although MERS is said to have ended in Korea, about 100 people who have been to the Middle East are treated as suspected MERS patients every year. COVID-19 has much greater spreading power than MERS."
- When do you think it will end globally?
"There is a high possibility that it will not end within this year. The world experienced two pandemics so far, which were the influenza pandemics, including the Hong Kong flu and the swine flu. They started at the same time and ended simultaneously. However, the Covid-19 pandemic is like a domino. Even if COVID-19 ends in Korea, it is not over. It can go around in other countries like dominoes and then come back to our country again."
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