The Department of Medical Sciences has confirmed that Influenza A(H1N1)pdm09 was the most dominant flu strain detected in Thailand between January and October this year, reassuring the public that genomic monitoring showed no signs of antiviral drug resistance.
Dr. Adisorn Wathanasak, director-general of the Department of Medical Sciences, stated that surveillance data gathered by the Thai National Influenza Center, a World Health Organization (WHO) regional reference laboratory, analysed 8,734 patient samples during the ten-month period.
Out of the total samples collected, 1,278 tested positive for influenza, representing a positivity rate of 14.63%.
Influenza A(H1N1)pdm09 accounted for the majority of detections, comprising 704 cases or 55.09% of all positive samples. This was followed by Influenza A(H3N2) with 306 cases (23.94%) and Influenza B of the Victoria lineage with 268 cases (20.97%).
The dominance of A(H1N1)pdm09 surged even further in October, where it represented 115 out of 122 positive cases, or 94.26%, from 581 patient samples submitted during the month. In contrast, Influenza A(H3N2) dropped to 2.46% (3 cases) and Influenza B accounted for 3.28% (4 cases).
Detailed genetic sequencing showed that the A(H1N1)pdm09 clade 6B.1A.5a.2a.1 has increased significantly since June and remains the primary circulating subtype.
Meanwhile, the K clade was identified as the main variant for Influenza A(H3N2) throughout the surveillance period, while the V1A.3a.2 clade was the main variant detected for Influenza B.
Regarding drug resistance monitoring, laboratory analysis of the Neuraminidase (NA) gene across tested specimens, including 127 samples analyzed specifically in October, showed no evidence of mutations that indicate resistance to antiviral therapies.
Crucially, tests confirmed the absence of the H275Y mutation in A(H1N1)pdm09, which is linked to Oseltamivir resistance. No other genetic mutations associated with reduced sensitivity to neuraminidase inhibitors were found across any of the circulating strains.
Dr. Adisorn emphasised that ongoing surveillance of viral clades, genetic alterations, and drug resistance remains essential for evaluating transmission trends and supporting public health interventions.
He advised members of the public to maintain good personal hygiene and follow public health guidelines to reduce the risk of infection and prevent the spread of the virus.
