South Korea's health authorities said Tuesday the country has not found additional cases of a more transmissible COVID-19 variant after it confirmed its first three cases of the strain in arrivals from the United Kingdom a day earlier.

The Korea Disease Control and Prevention Agency (KDCA) said 17 people who were found to have been in close contact with the three confirmed patients all tested negative for COVID-19.

British analysis suggests the new strain may be up to 70 percent more transmissible than the old variant. The new variant is believed to have first occurred in mid-September in London.

The KDCA reported Monday that three members of a South Korean family who arrived from the United Kingdom last week had the new COVID-19 strain. The family was immediately quarantined after their arrival in the country.

The KDCA said the 17 people who were tested had been in contact with the family inside the plane and that they are currently under quarantine and being monitored for possible symptoms.

To prevent the spread of the new COVID-19 variant, South Korea has strengthened anti-infection measures, such as conducting additional testing for foreign arrivals prior to the end of their self-quarantine period. All foreign arrivals who enter South Korea must be quarantined for two weeks.

The country has also suspended flights arriving from the United Kingdom until Jan. 7 of next year and is conducting additional tests to check for the new COVID-19 variant among arrivals who test positive for COVID-19 and are from the United Kingdom and other countries that have reported the new strain.

South Korea has also made negative COVID-19 test results compulsory for arrivals from the United Kingdom and South Africa from the start of next year and has decided to suspend issuing new visas for arrivals from the two countries starting Tuesday, with the exception of diplomatic, official service or humanitarian reasons.

South Korea's daily coronavirus cases bounced back to over 1,000 on Tuesday after three days despite tougher virus curbs, while daily virus deaths hit a fresh record high of 40. (Yonhap)