Health officials have been tracing the movements of a Myanmar woman and her child after the baby tested positive for the coronavirus disease after returning home from Thailand.
Dr Suwannachai Wattanayingcharoenchai, director-general of the Department of Disease Control, said yesterday that contact tracing was underway.
Myanmar also imposed a curfew in Myawaddy town opposite Thailand's Tak province yesterday.
The two-year-old child reportedly left Mae Sot district of Tak with his mother on Sept 4. His infection was confirmed in Myanmar on Sunday.
Dr Suwannachai said that the department checked information with the Mae Sot-Myawaddy immigration checkpoint and found that the mother and child did not pass the official border crossing and might have used any of about 50 uncontrolled natural crossings there.
Health officials collected samples from 2,635 Thai and foreigners in Mae Sot on Sept 8 and 9 and no one tested positive for Covid-19, he said.
After the investigation is done, people who had contact with them will be identified and tested, Dr Suwannachai said.
Tanarak Plipat, deputy director-general of the Department of Disease Control, said the department has asked the Interior Ministry to instruct 10 provinces bordering Myanmar to take measures to prevent the entry of illegal immigrant workers in the wake of a surge of Covid-19 infections there.
Provinces where Myanmar migrant workers stay have also been told to keep an eye out for workers suffering respiratory and lung diseases, Dr Tanarak said.
Myanmar reported 307 new cases of Covid-19 on Tuesday, its highest daily toll since the start of the pandemic, and another 134 yesterday, bringing the total to 3,636 cases and 39 deaths.
Myanmar had gone weeks without a case of local transmission before an outbreak in mid-August in Rakhine that has spread across the country.
Somkiat Aujeemid, who runs tourism businesses in Myanmar's southern city of Myeik, opposite Thailand's Prachuap Khiri Khan, said local health officials reported three new Covid-19 cases there, raising the total to five.