Medical staff wait to collect swab samples from residents for COVID-19 test in Qingdao, east China's Shandong Province, Oct. 14, 2020. (Xinhua/Li Ziheng)

The Taiwan epidemic control authority confirmed Wednesday that a Taiwan resident who tested positive for coronavirus upon his return to the island from Jiangsu Province in the Chinese mainland on October 11 was actually not infected with COVID-19. 

The positive result was for another man who arrived at the island on the same day from France. The authority said that the inspection department confused their saliva samples collected at the airport, according to Taiwan media outlet Liberty Times.

The saliva sample of the man who came back from Jiangsu appeared to be positive at the airport. However, samples collected in later tests on the following days were all negative. The man’s antibody test also returned a negative result, according to the head of Taiwan’s health department Chen Shih-chung.

The authority then started an investigation into the whole inspection process and carried out another round of tests on 31 saliva samples on October 16, which finally showed that the man who returned from France had the coronavirus.

DNA tests showed that the saliva sample of the man from Jiangsu, which was collected at the airport on his arrival, actually belonged to the man from France. Their samples were misplaced in the lab, Chen said.

However, the man from Jiangsu had already started self-isolation because of his “positive” result. Chen said that the health department has explained the matter to him and he accepted the explanation.

The man from France, also a Taiwan resident who has been working in France for a long time, developed symptoms during home isolation and was diagnosed with COVID-19 on October 19, reports said.

The Taiwan authority announced the “confirmed case” from Jiangsu on October 13, saying that the man had a runny nose, a cough and other cold symptoms, Taiwan media reports said. 

After that, the center of disease control and prevention in Kunshan started environmental monitoring and disinfection where the man stayed, and carried out serum and throat swab sampling tests on people he had contact with. All the 1,970 samples returned negative results, Xinhua News Agency reported October 14.

Moreover, a total of 40 close contacts of the man were found, and all their serum and throat swab test results were negative.