Four Chinese citizens who came from China to Bangladesh on Monday were sent to isolation as they were detected with Covid-19 during health screening at the Hazrat Shahjalal International Airport.

Their samples were sent to the Institute of Epidemiology, Disease Control and Research (IEDCR) for genome sequencing, the result of which is pending, IEDCR Director Professor Dr Tahmina Shireen said.

"Coronavirus infection was detected in the Chinese nationals through the antigen test," she said, adding that the four Chinese nationals were sent to Mohakhali DNCC Hospital for isolation.

Assistant Director of the Airport Health Department Dr Shahriar Sajjad told The Business Standard that the faces of those four passengers were red. When their antigens were tested, they were diagnosed with the coronavirus.

Dr Shahriar also said the passengers carried the certificate of Covid negative to RT-PCR from China.

"As they were suspected of having some symptoms at the airport, they were tested for antigens when they were diagnosed as positive. The IEDCR has been informed about their result of being positive for Covid and all four have been sent to isolation," he said.

The Covid-19 RT-PCR test will also be done for all those four patients, he added.

The four Chinese nationals were the first detected Covid-19 positive in the antigen tests over the last one year at Dhaka airport. The flight China Eastern, number MU2035, reached Dhaka from Kunming in China.

National Technical Advisory Committee (NTAC) on Covid-19 member Professor Nazrul Islam suggested waiting for the RT-PCR test report of the four Chinese citizens who were tested positive in the antigen tests.

"It was a good decision to isolate them quickly. If the RT-PCR test result is positive, genome sequencing should be done to see whether they are infected with the Omicron sub-variant BF.7," he said, adding: Since the sub-variant of Omicron is highly contagious, vigilance must be maintained at the port of entry so that the infected individuals can be identified immediately and sent to isolation.

On 25 December, the Directorate General of Health Services (DGHS) instructed all air, land and sea ports to intensify screening in the backdrop of a rise in the number of new Covid-19 cases in several countries, including China and India.

All ports have also been instructed to do rapid antigen tests of the infected persons and isolate them. The newly discovered BF.7 variant is Omicron's sub-variant, four times more contagious than the other variants.