Thailand has detected its first case of the Omicron variant of the coronavirus.

Thailand’s Ministry of Public Health on Monday announced the country’s first case of the Omicron variant, in a U.S. citizen who entered Thailand nearly a week ago. The 35-year-old American had been living in Spain for a year, officials said and was inoculated in June with the Johnson & Johnson vaccine.

The confirmed case in the man, who had arrived on November 29, makes Thailand the 47th country to have found the new variant, an official said, adding that the patient had mild symptoms.

Last month, Thailand became one of the first Southeast Asian countries to reopen its borders to fully vaccinate tourists, allowing arrivals by air from 63 countries. Fully vaccinated visitors from those areas must take a P.C.R. test on arrival and stay one night in an approved hotel while awaiting the result.