Two people in Singapore who came back from the UK have been preliminarily tested to have a new Covid-19 strain that is circulating there, the Ministry of Health said in a statement.

One of the people that initially tested positive for the potentially more contagious virus strain is a Singapore Airlines Ltd. pilot, who traveled to the UK for work from Dec. 19 to 22. While his test taken on Dec. 23 came back negative, he developed a fever three days later and was confirmed to have Covid-19 on Dec. 29.

The second case is a work pass holder who arrived from the UK on Dec. 7. He ended his 14-day quarantine on Dec. 21 after testing negative on Dec. 17. He later developed body aches and was tested positive for the virus on Dec. 29.

The two cases have tested preliminarily positive for the B117 strain, and further confirmatory tests will be conducted, the ministry said.

Cases of the new Covid-19 strain could pose a challenge to Singapore, which has been lauded for its success in quelling the pace of infections in the community. It first detected this new strain last week in a Singaporean student studying in the UK. The Southeast Asian nation has imposed tougher border restrictions including barring entry and transit for those who have travel history to the UK in the past 14 days, though citizens and permanent residents are allowed to return.

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“Epidemiological investigations are in progress,” the ministry said in the statement late Wednesday. “In the meantime, all the identified close contacts of the cases have been isolated and placed on quarantine, and will be tested at the start and end of their quarantine period so that we can detect asymptomatic cases.”

Tightened Measures

The Civil Aviation Authority is tightening measures to ensure the safety and well-being of air crew and to safeguard public health in Singapore after the Singapore Air pilot tested positive together with a separate case of a cabin crew member, Straits Times reported, citing the authority.

Air crew returning from flights in high-risk destinations will be required to take three tests -- one on arrival, another on the third day and one on the seventh day. It will also require air crew on layover to further minimize contact with locals, with food delivered through room service left outside the room at the door instead of being handed over.

Preliminary investigation by the CAAS showed that the two cases had adhered to the mandated in-flight and layover measures, including wearing a mask, minimizing contact with passengers and locals, and staying in their hotel rooms, the report said.

Air crew traveling to and from South Africa will also have to wear full personal protective equipment, including N95 masks, face shields, protective gowns and gloves, according to the report.