A shopping mall and a bar in Chiang Mai have been closed while anxious officials test more than 300 people for Covid-19.
The urgent action follows the revelation that a 29-year-old Thai woman caught the virus in Myanmar and despite going down with a fever, returned to Thailand and visited several places before finally going to hospital and testing positive for the coronavirus. She was able to do so without entering quarantine, which has alarmed the authorities.
The Department of Disease Control (DDC) said it will take two weeks to establish whether the woman is a super-spreader after it discovered that she came into contact with at least 326 people. The DDC added that strong legal action must be applied in this case after finding that she was not in the quarantine system.
Opas Kankawinpong, acting chief of the DDC, said on Saturday the timeline of the woman's movements was quite clear: she was infected while in Myanmar from Oct 24 to Nov 23, when she began to develop a fever and diarrhoea.
The DDC's Chiang Mai provincial committee says the woman entered the country illegally on Nov 24 through a natural border in Chiang Rai's Mae Sai district and took a public bus the same day to her condo in Chiang Mai.
Later she met her friends at a pub in the Santitham area, and also went shopping at CentralFestival Chiang Mai, even while suffering from the fever.
CCTV camera footage shows she wore a face mask at least some of the time she was in public areas.
"My big question is why she didn't attend the quarantine system. All returnees must enter the 14-day quarantine with no exception," said Dr Opas.
"Illegally entering Thailand carries a heavy punishment. It will be necessary to apply all immigration and public health laws in this case. It is dangerous to the community and the country. We need all stakeholders to prevent it."
Dr Opas also urged people to contact authorities immediately if they knew of anyone who was breaking the laws in this regard. The infected woman was tested for the virus on Nov 26 and admitted to Nakornping Hospital, Chiang Mai.
According to the DDC, she was admitted suffering from a fever and had lost her sense of smell, a common symptom found in Covid-19 patients.
A disease investigation team found that 105 people are at high risk of contracting the virus from the woman, including friends that shared a cigarette with her, 40 bus passengers, 55 bar staff and six people from the department store.
A further 140 people are regarded as being at low risk: 138 from department stores, two from the pub, nine medical staff and 72 around the community.
Sophon Iamsirithavorn, director of the Division of Communicable Diseases, said the investigative team had since Thursday contacted those people at highest risk and put them under 14-day surveillance. He suggested anyone who thinks she came into contact with her should be alert for any sign of a fever or be tested for the virus at a nearby hospital.
CentralFestival Chiangmai closed for a major cleaning operation on Saturday and will reopen today.
Meanwhile, the Chiang Mai Municipality on Saturday sprayed chemicals into pubs along the Santitham area to kill the virus and ordered them to shut for a while. Chiang Rai governor Prajol Pratsakul said he had made contact with various agencies to prevent illegal entry along the border but does not yet know how the woman sneaked into the country.