Ministry of Public Health officials are on high alert after at least one foreign national was detected carrying an Omicron sub-variant with the potential to cause severe infections, according to the ministry's Department of Medical Sciences.
Supakit Sirilak, director-general of the DMSc, on Monday said Omicron has become the dominant coronavirus strain in Thailand, with the BA.2 sub-variant attributed to 97.6% of infections in the country.
The ministry has paid heed to the World Health Organization (WHO)'s warning of the emergence of three infectious Omicron sub-variants -- BA.4, BA.5 and BA.2.12.1, he said.
Omicron sub-variants, BA.4 and BA.5, were first discovered in South Africa in January and February, respectively, he said, while BA.2.12.1 was discovered in the United States in February, he said.
However, sub-variants BA.4 and BA.5 have since been found spreading in many countries, including Botswana, South Africa, Germany and Denmark, while BA.2.12.1 has been detected in Canada and India, he said.
In Thailand, whole genome sequencing (WGS) recently confirmed that a Brazilian national has contracted BA.5, while two others, an Indian and a Canadian, have contracted BA.2.12, he said.
As of now, sub-variants BA.2.12.1 and BA.4 have not yet been discovered in Thailand, Dr Supakit said.
The WGS findings have shown that some parts of the genome sequences of BA.4 were found to be similar to both BA.1 and BA.2 sub-strains, he said.
The spike protein may also undergo mutation similar to how the previous Delta variant had evolved, he said.
Dr Supakit noted that those infected with BA.1 have weak immunity against BA.4 and BA.5 sub-variants. However, fully vaccinated people have stronger immunity against the two sub-variants, he said.
Gisaid, a global data science initiative, also reported that the hybrid species of the coronavirus have not yet been found in Thailand, Dr Supakit said.
The DMSc chief said department offices nationwide will closely monitor coronavirus infections for any presence of BA.4, BA.5 and BA.2.12.1.