Thailand has confirmed six new imported cases of the novel coronavirus, including three Thai men who were previously infected but had been certified virus-free before flying from Singapore.
The Centre for COVID-19 Situation Administration (CCSA) said on Sunday the three men, aged 43, 53 and 56, tested positive for the virus after arriving on Friday.
An official at the CCSA call centre said they had contracted the virus in Singapore, but then made a full recovery. They applied for and received certificates of good health from the Thai embassy before boarding the flight, as required for every person flying into Thailand.
The men were tested again upon arrival and diagnosed with COVID-19.
It was not immediately clear how the course of events could have taken place. The final Singapore tests could have returned a false negative or the tests on arrival in Thailand a false positive. What would ring alarm bells is a third scenario – the men caught the disease, recovered and then caught it again. That would imply they had no immunity to the disease even after contracting it, which could render any vaccine ineffective.
The CCSA said that three other imported cases were recorded on Sunday.
Two Thai nationals, a 46-year-old housemaid and a woman aged 83, were found infected during quarantine on Friday after returning from the United States on Monday.
The sixth case was a 46-year-old Frenchman who arrived in Thailand on Tuesday from the United Kingdom. He tested positive on Friday while in quarantine at a private facility in Bangkok.
He was a language teacher at a private school in the country.
The new infections, all asymptomatic, took the total tally of infections in the country to 3,444, while no new fatalities were reported.