Taipei, Feb. 23 (CNA) Two men in Taiwan with no recent history of overseas travel have contracted the novel coronavirus disease (COVID-19), bringing the number of confirmed cases in the country to 28, with one death, the Central Epidemic Command Center (CECC) said Sunday.

The two new patients are a father and son in their 80s and 50s, respectively, who live in northern Taiwan, CECC Deputy Commander Chuang Jen-hsiang said at a press conference.

The father, who suffers from high blood pressure, diabetes, and kidney problems, developed a cough and a runny nose on Feb. 6, according to Chuang.

Three days later, the man was admitted to a private room at a hospital after he came down with a fever and was diagnosed with pneumonia, Chuang said.

The patient was transferred to an intensive care unit on Feb. 16 and to a negative-pressure isolation room on Feb. 20, as doctors suspected that he had tuberculosis, Chuang said.

He was tested on Feb. 21 for COVID-19 and was confirmed Sunday as the 27th case in Taiwan, Chuang said.

Health authorities have been testing people who had come in contact with the man and were showing symptoms of COVID-19, including his son, who was also found to be infected with the disease, according to Chuang.

The son, now listed as Taiwan's 28th case, had visited a doctor on Feb. 4, complaining of a fever, cough and runny nose, Chuang said.

When the symptoms did not abate, the son went to the emergency room on Feb. 8 and was diagnosed with pneumonia. He visited the doctor two more times, on Feb. 11 and Feb. 18, was tested for COVID-19 on Feb. 21, and was confirmed on Sunday to be infected, Chuang said.

While the two men had no recent history of overseas travel, the CECC learned that the father has another son whose job takes him to China frequently and who had shared a meal during the Lunar New Year holidays with a friend who had recently returned from China, according to Chuang.

That son developed respiratory symptoms on Jan. 29 and was recently tested for COVID-19, but the results have not yet been released, Chuang said.

Although that son returned from his last trip to China on Dec. 2, 2019, it is highly likely that he was the source of the infection of his father and older brother, particularly as the father was staying with both sons, alternating between the two residences, according to Chuang.

Meanwhile, the CECC has so far identified 115 medical personnel who came in contact with the father when he was in hospital, and 40 of them have been tested for COVID-19 and are awaiting the results.

With the confirmation of the two new COVID-19 cases on Sunday, the total number in Taiwan has climbed to 28, three of which have not been traced to a source of infection.

Apart from the father and son, the 24th case is a woman in her 60s, who was diagnosed on Feb. 19 and had no history of overseas travel in the past two years.

The CECC has since tracked down 533 people who had come in contact the woman, and two of them -- her daughter and granddaughter -- have tested positive for the disease.

Another 192 of that number have been tested and 173 have been cleared, while 19 are still awaiting their test results, according to the CECC.

CECC advisor Chang Shan-chwen (張上淳) said the three cases of unknown sources indicated sporadic community-level transmission of the coronavirus in Taiwan.