Nikhil Prasad Fact checked by:Thailand Medical News Team Nov 09, 2026 9 minutes ago
Thailand’s influenza surveillance has revealed a dramatic rise in Influenza A(H1N1)pdm09, which accounted for more than 94 percent of laboratory-confirmed flu infections in October. However, health authorities have offered reassurance that genetic testing has detected no mutations associated with resistance to commonly used antiviral medications.
Influenza A(H1N1) accounted for over 94 percent of Thailand’s October flu detections, although surveillance found no antiviral resistance mutations.
H1N1 Emerges as Thailand’s Leading Influenza Strain
Thailand’s Department of Medical Sciences reported that the Thai National Influenza Center, a World Health Organization regional reference laboratory, examined 8,734 patient samples between January and October.
Of these, 1,278 samples tested positive for influenza, representing a positivity rate of 14.63 percent.
Influenza A(H1N1)pdm09 dominated with 704 cases, accounting for 55.09 percent of positive samples. Influenza A(H3N2) followed with 306 cases, or 23.94 percent, while Influenza B Victoria lineage accounted for 268 cases, or 20.97 percent.
October Data Reveals Overwhelming H1N1 Dominance
October surveillance highlighted an even more striking shift in circulating influenza strains.
Among 581 specimens tested, 122 were influenza-positive, representing approximately 21 percent.
Of these infections, 115 involved A(H1N1)pdm09, accounting for 94.26 percent. A(H3N2) represented just three cases (2.46 percent), while Influenza B accounted for four cases (3.28 percent).
This
Thailand Medical News report highlights how rapidly one influenza subtype can become predominant within surveillance samples, although these figures do not necessarily represent Thailand’s entire infected population.
Genetic Sequencing Identifies Dominant Viral Clades
Genomic surveillance revealed that the A(H1N1)pdm09 subclade 6B.1A.5a.2a.1 increased substantially from June onward, becoming the principal circulating genetic group.
Meanwhile, the K clade predominated among A(H3N2) detections, while V1A.3a.2 remained the principal Influenza B genetic lineage.
Antiviral Resistance Testing Provides Reassurance
Importantly, neuraminidase gene analysis, including 127 specimens examined during October, identified no known resistance-associated mutations.
Scientists specifically confirmed the absence of H275Y, a mutation associated with reduced susceptibility to oseltamivir in A(H1N1)pdm09.
No other mutations indicating reduced sensitivity to neuraminidase inhibitors were detected among the examined strains.
Nevertheless, genetic susceptibility findings cannot guarantee successful treatment in every patient.
Continued Vigilance Remains Essential
Department director-general Dr. Adisorn Wathanas
ak emphasized that continuous genomic surveillance remains vital for identifying emerging variants and potential drug resistance.
Although current findings support the continued usefulness of neuraminidase inhibitors, the overwhelming October dominance of H1N1 reinforces the importance of vaccination, hygiene, early clinical assessment, and ongoing monitoring. Surveillance must continue because viral evolution could eventually alter treatment susceptibility, while the absence of resistance does not eliminate the threat of serious influenza complications.
Reference:
https://www.dmsc.moph.go.th/th/detailAll/3915/nw/25 
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