In a statement issued on Tuesday, the Centre for Health Protection said the 25-year-old woman, who came to Hong Kong in March, had been diagnosed with the coronavirus in the United States in January.
Authorities say she is asymptomatic, adding that she tested negative after being sent to hospital, with antibodies found in her sample.
“The test result also revealed that the specimen did not carry the N501Y or L452R mutant strain”, the statement read.
“After examining the epidemiological, clinical and laboratory findings, this case is compatible with a re-positive case. The CHP is following up the case with the US health authority.”
Meanwhile, one new imported case has been reported, involving a 56-year-old man who flew in from Russia.