The discovery of the first cases of community transmission of more contagious coronavirus variants is putting authorities on high alert, prompting worries that this will set back South Korea’s efforts to curb the ongoing third COVID-19 wave and may signal the start of another more serious wave.

Prime Minister Chung Sye-kyun urged officials Thursday to increase their efforts to prevent additional community transmission of variants traced to the UK, South Africa and Brazil.

The Korea Disease Control and Prevention Agency said Wednesday that it had identified five more cases of the highly contagious variants, all of which were domestically transmitted, bringing the total number of cases so far to 39.

Four of the people who tested positive were confirmed infected with a variant traced to Britain, after coming into contact with relatives who were under self-quarantine in their homes.

Authorities are investigating 34 more people who came into contact with the same relatives to see if they too are infected with the variant.

The other person, who tested positive for the South Africa variant, was infected after coming into contact with a family member who had traveled overseas.

Officials are running checks on all 136 people who came into contact with those with the variants, warning that the number of cases could see an explosive rise in the coming days.

The news has alarmed officials as it may mean that the mutated virus variants were already spreading within the population much earlier, before the first cases were detected.

The head of the KDCA’s epidemiological analysis team, Park Young-joon, said in a press briefing Thursday that it is “only a matter of time for the virus variants to speedily increase their presence in the country.”

Health Ministry official Yoon Tae-ho said officials and experts need to prepare for another virus wave that could start next month, as more transmissible variants have officially started to spread within communities.

And with the Lunar New Year holiday approaching soon, disease control officials fear that the new variants could spread even further as thousands of people are expected to travel and visit relatives during the four-day weekend.

The country has banned passenger flights from Britain until Feb. 11 to block the new variant from Britain, and officials are running next-generation sequencing tests on arriving passengers from Britain and South Africa.

All foreign arrivals must present the results of a negative PCR test taken within 72 hours of their departure for Korea.

By Ko Jun-tae (ko.juntae@heraldcorp.com)