Covid-stricken chief secretary-designate Eric Chan and his wife aren't showing many symptoms of the virus, RTHK learnt on Friday.

The government announced on Thursday that Chan, who's currently Chief Executive Carrie Lam's top aide, and constitutional and mainland affairs minister Erick Tsang have come down with the disease and that both men are being isolated.

Tsang told TVB news that he had no idea where he contracted the virus.

"I don't really feel unwell. There's no fever or other symptoms. I did the PCR test because I was going to attend the [July 1] ceremony and the result came back positive," he said.

Asked if his infection may affect the swearing-in ceremony, Tsang said it depends on whether he has recovered by then, as well as on the arrangements of the organisers.

Meanwhile, sources told RTHK that Chan and his wife, who is also infected, have very few symptoms.

Chan and Tsang are the most senior government officials so far to catch the coronavirus and their infections have cast a shadow on the July 1 ceremony, which it is thought could be attended by a state leader.

A government spokesman said officials are closely monitoring the situation with a view to making appropriate arrangements.

He also said that the CE last came into contact with Chan on Monday, though they only spoke briefly with masks on and kept a distance from each other. Lam, therefore, is not considered to be a close contact, the spokesman said.

Lam didn't have any contact with Tsang in the past week or so, the spokesman added.

Incoming chief executive John Lee last appeared with Chan and Tsang on Sunday when he introduced his cabinet to the media.

The government spokesman said Lee last met the pair a couple of days ago, and Lee tested negative for Covid on Wednesday.