On Jan. 31, 2020, the World Health Organization declared the outbreak of novel coronavirus 2019 (2019-nCoV) a public health emergency over the world but did not restrict international transportation of humans and trade. However, many countries began to limit entrants from China after the declaration.

In Korea, a total of 16 patients of pneumonia or respiratory infection by 2019-nCoV had been confirmed by the Korea Centers for Disease Control and Prevention (KCDC) by Feb. 4, 2020 (Table 1). The KCDC is closely and actively monitoring clinical patients and people who contacted confirmed patients.

We need to pay particular attention to three of these confirmed patients -- patient numbers 1, 3, and 12.

The first patient had pneumonia three days after he showed symptoms, although her condition was stable. During the first three days, she did not develop any clinical features suggesting pneumonia. If an early high-resolution computed tomography scan of the lungs had not been taken, pneumonia would not have been diagnosed. This indicates that the possibility of 2019-nCoV pneumonia cannot be excluded based only on the clinical clues. And the patient remained on a severe clinical course with high oxygen demand for more than two weeks. Based on this clinical course, although the 2019-nCoV is tentatively known to have less severity of the disease than SARS, the virulence of the disease needs to be evaluated more carefully.

The third patient was meaningful in that he caused a secondary infection to the sixth patient for the first time in Korea. The sixth patient then infected two of his family members -- the 10th and 11th patients -- to establish a tertiary infection. This raises the concern that the 2019-nCoV could spread significantly to the community shortly. All of them were on the KCDC list, and therefore they were detected rather early.

The 12th patient was a secondary infection case in Japan and had never been to Wuhan. Therefore, he easily entered Korea without strict screening at the airport and led his daily life for more than 10 days without any restriction until the 2019-nCoV infection was confirmed. The 12th patient also has the potential to spread the disease as widely as the third patient to the community. Actually, the 14th patient is his wife.

Many patients shared common exposure.

The third, seventh, eighth, and 15th patients had a history of working or staying at “The Place,” which housed many Korean stores within the Wuhan International Fashion Center. They might have been exposed to the virus at the center, and seventh and eighth patients moved from China on the same airplane.

The problem is that seventh, eighth, and 12th patients were not on the list of active monitoring by the KCDC. It suggests that there are more potential patients, although the KCDC is actively monitoring all of the people on the list of direct or indirect contacts with the confirmed patients. As Professor Yoo Jin-hong mentioned in the last issue of the Journal of Korean Medical Science, clearing the present outbreak of 2019-CoV in Korea may last longer than expected. The complete elimination of the 2019-CoV transmission depends critically on the early detection of patients out of the KCDC list.

At this point, we must doubt whether the defenses thus far have been successful.

Screening with the current guidelines applied only to those with symptoms has reached its limit. Although evidence is still insufficient, claims about the possibility of transmission from asymptomatic cases continue to be published.

More than 6,000 people have already come to Korea from Wuhan during the Lunar New Year holiday. Given the incubation period, the next couple of weeks are essential. If the virus has a large amount of viral shedding before symptoms are evident, it has likely been widespread in our community.

Now, serious consideration should be given to the temporary ban on visitors or the high-level quarantine of all entrants from China. It is reported that about 20,000 visitors come from China every day. By Feb. 2, the outbreak of 2019-nCoV was still progressing seriously in China, with more than 15,000 patients and 361 deaths according to reports of the Chinese Committee of Hygiene. No one can estimate how many patients may appear soon because thousands of patients and several tens of deaths are added every day in China. Considering our demographics and population mechanics, including Chinese visitors, we should seriously worry that the virus has already been disseminated into our community over the currently known levels of exposure.

Entry ban or high-level quarantine does not constitute the violation of human rights, nor is it irrational racism. This is a serious health security emergency in Korea as well as in the world. The government must discern this security agenda and decide how to upgrade enforcing the present national strategy against the 2019-nCoV outbreak as soon as possible.

Quarantine at the immigration for asymptomatic visitors from epidemic areas is an effective preventive method that has been historically proven and should be actively applied. However, the technique looks not enough to end the present outbreak. Besides, because the possibility of dissemination within our community cannot be ruled out, the more active preemptive containment policy is required targeting both domestic and international transmission.

Perhaps this is the last chance for us to contain further spread of the disease. If it spreads further, we have no way to stop the virus.

This article was originally published in the Journal of Korean Medical Science.—Ed.