Commuters wait at a traffic signal in the Central district of Hong Kong, June 7, 2021. (PHOTO/BLOOMBERG)

HONG KONG – Hong Kong’s streak of infection-free days came to an end on Thursday with the first untraceable local COVID-19 case in nearly two months, just as the government began easing restrictions on international travel.

The new case is somewhat of a mystery: a 43-year-old construction worker with no symptoms and no recent travel history, but COVID-19 antibodies in his blood despite not having been vaccinated, said government officials.

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The findings are “compatible with a re-positive case previously undiagnosed,” according to a government statement on Thursday. The man’s virus load is so low that genetic sequencing cannot be performed to determine which strain is involved.

The man’s virus load is so low that genetic sequencing cannot be performed to determine which strain is involved

The man lived at Block A of Tung Lo Court in Sham Shui Po and worked at 248 Queen’s Road East and Shiu Kin Lane in Wan Chai. His last working day was Tuesday.

Other residents living in the same building, his colleagues and people who’ve visited the same places he did during the incubation period must now go for compulsory testing as the government tries to head off the risk of the virus circulating locally.

The incident comes as Hong Kong plans to allow vaccinated tourists from all but 10 places in the world to enter the city starting on Aug 9. Residents and other travelers with positive antibody tests will be allowed shorter stays in hotel quarantine. The easing of some of the world’s tightest border curbs is intended to speed the financial hub’s return to its global business-oriented roots.

The financial hub also reported five imported cases on Thursday. They were a 24-year-old woman flying in from Ireland, a 71-year-old man from Cambodia, a 37-year-old man from the United States, a 16-year-old teenager from Thailand and a 35-year-old woman from Russia.

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Among them, the travelers from Ireland and the United States have been fully inoculated with the BioNTech vaccine in Hong Kong. The man from Cambodia has been fully vaccinated with the AstraZenaca vaccine in Cambodia, the health authorities said.

With Bloomberg inputs