The Central Epidemic Command Center (CECC) yesterday reported no new confirmed cases of COVID-19, and reiterated that the nation’s testing capacity, as well as the number of conducted tests, are sufficient.

Minister of Health and Welfare Chen Shih-chung, who heads the center, said that as of yesterday, the number of confirmed cases remains at 447, of whom 438 have been released from isolation and seven have died.

“Two infected patients remain hospitalized for treatment and we wish them a speedy recovery,” Chen said.

CECC advisory specialist panel convener Chang Shan-chwen said that the two are asymptomatic cases.

One of them returned from Bangladesh and was reported by the CECC on June 18, and the other returned from Guatemala and was reported on Thursday last week, Chang said, adding that they are both in a stable condition.

The CECC last week reported that a Japanese woman in her 20s who had studied in southern Taiwan since late February had tested positive for COVID-19 upon her return to Japan on June 20, prompting questions about whether Taiwan should conduct more tests to find asymptomatic cases.

Centers for Disease Control (CDC) Deputy Director-General Chuang Jen-hsiang, who is also the CECC spokesperson, said that the polymerase chain reaction (PCR) diagnostic tests conducted on 123 people who had come into direct contact with the student all returned negative results.

The contacts have also been tested for antibodies and more than 60 of them returned negative results so far, Chuang said.

The PCR tests showed low viral loads and all of the people who had come into direct contact with the student in the 14 days before she was confirmed with COVID-19 also showed negative results, Chang said.

It is possible that the student was infected prior to the 14-day period, he said, but added that the people she came into direct contact with before then were more or less the same group of people who have been tested.

“We are concerned about this case and want to clarify it through the close contacts,” Chen said, adding that the contacts have been placed under home isolation.

The antibody tests would help health officials understand the possible route of transmission, which can be helpful for policymaking, he said.

Chen cited several scenarios to explain why Taiwan does not need to conduct more tests in local communities, and why conducting tests on all arriving passengers at airports might not be safer than the current policy.

The virus can be detected two days before the onset of symptoms, Chen said.

Citing the nation’s 340 imported symptomatic cases as an example, he said that 119 of them (35 percent) were detected more than two days after they arrived in Taiwan, so allowing entry to people who test negative at airports upon arrival without placing them in quarantine might cause infected people to enter local communities.

Using the same example, Chen said that 93 percent and 96 percent of the imported cases were detected within five days and seven days after arrival respectively, so if all arriving passengers are quarantined for at least five or seven days, the risk of overlooked cases could be reduced to 7 or 4 percent.

The positive rate in COVID-19 testing is as low as 0.43 percent in Taiwan, which means that, on average, one out of every 167 people who were tested was confirmed with the disease, Chen said.

The rate is one of the lowest in the world, and the WHO suggests nations to consider easing lockdown measures only if they have a rate of less than 5 percent, he said.

The tests carried out in Taiwan have been sufficient, he said, adding that expanding testing would have a significant social cost, with a very limited effect on disease prevention.