Taipei, Sept. 17 (CNA) Three Taiwanese nationals who work overseas -- in Myanmar, the United Kingdom and the Philippines, respectively -- have tested positive for COVID-19 following their recent return to Taiwan, the Central Epidemic Command Center (CECC) said Thursday.

The three new cases brought the total number recorded in Taiwan to 503 since the start of the pandemic late last year, according to CECC data.

One of the new cases is a woman in her 40s, who traveled to Myanmar in February for work purposes and returned to Taiwan on Sept. 13, the CECC said.

Although the woman showed no symptoms of COVID-19 upon arrival, she was tested because she told airport personnel that she had gone to dinner with someone in Myanmar who was later confirmed to have the disease, the CECC said.

The woman's test came back positive on Thursday, and she has been transferred from a designated quarantine center to hospital, the CECC said.

In its contact tracing, the CECC said, it has identified 23 people who had contact with the woman on her flight to Taiwan -- a friend, five crew members, and 17 passengers.

The passengers and the woman's friend are currently in home quarantine, while the crew members have been instructed to follow self-health management protocols, as they had been wearing protective gear on the flight, the CECC said.

Meanwhile, the patient who returned from the U.K. is a woman in her 20s, who went there in February 2019 to work, according to the CECC.

She showed no symptoms of COVID-19 upon arrival in Taiwan on Sept. 6 but developed a mild sore throat on Sept. 10 and diarrhea, stomach pains, and a runny nose a few days later, the CECC said.

She was tested for the disease, after alerting health authorities to her symptoms, and was confirmed Thursday to be infected, the CECC said.

It said that since the woman had no symptoms on arrival and went directly to a quarantine hotel, no contact tracing was being done in her case.

The third case reported Thursday is a man in his 30s, who had traveled to the Philippines in March for work.

Three days before his return to Taiwan on Sept. 13, he developed a runny nose, dry throat, cough, tightness in the chest, and a reduced sense of smell, but he did not seek medical attention in the Philippines, the CECC said.

He traveled back to Taiwan on the same flight as Case 500 -- a woman from the Philippines who was confirmed Wednesday to have the disease -- but they did not sit near each other on the flight, according to the CECC.

The man reported his symptoms upon arrival and was tested for COVID-19, but the results were negative, the CECC said. He was tested again on Wednesday, because his symptoms persisted, and the results came back positive on Thursday, according to the CECC.

As no passengers had sat near the man on the plane, the CECC said, it has advised only the nine crew members on the flight to adhere to self-health management protocols.

To date, Taiwan has recorded 503 cases of COVID-19, with 411 classified as imported. Of the total, 478 have recovered, seven have died, and 18 are in the hospital, the CECC said.

Globally, COVID-19 has infected over 29.8 million people in 187 countries and regions, with 941,863 fatalities, according to CECC statistics as of Thursday.