Serological Analysis of Human Pandemic Influenza (H1N1) in Thailand

The study was aimed at determining the prevalence of pandemic influenza (H1N1) 2009 among patients with respiratory tract diseases during July-December 2009 using real-time reverse transcription polymerase chain reaction. Haemagglutination inhibition (HI) assay was performed to detect antibody titres against pandemic influenza in 255 medical personnel, 307 members of the general population during the second week of December 2009 in Khon Kaen province, Thailand, and in 100 stored sera collected from people of different age-groups during 2008. The results showed that the pandemic (H1N1) 2009 had occurred during July-December 2009. The results of the HI test after the wave of this outbreak showed that 123 (48%) of the 255 sera collected from the medical personnel, 109 (36%) of the 307 sera obtained from the general population, and only two of the 100 stored sera from 2008 contained antibodies (HI titres ≥40) against pandemic influenza. Antibody against the pandemic (H1N1) 2009 was found in at least one-third of the population. In conclusion, the prevalence of virus and serological data obtained from the study can be used as the serological background level of the Thai population after the July-December pandemic. Finally, the serological data might be useful for outbreak-prevention and control strategies and for the management of vaccination for the pandemic (H1N1) 2009 in Thailand

Molecular Evolution of Human H1N1 and H3N2 Influenza A Virus in Thailand, 2006–2009

Annual seasonal influenza outbreaks are associated with high morbidity and mortality.To index and document evolutionary changes among influenza A H1N1 and H3N2 viruses isolated from Thailand during 2006-2009, using complete genome sequences.Nasopharyngeal aspirates were collected from patients diagnosed with respiratory illness in Thailand during 2006-2009. All samples were screened for Influenza A virus. A total of 13 H1N1 and 21 H3N2 were confirmed and whole genome sequenced for the evolutionary analysis using standard phylogenetic approaches.Phylogenetic analysis of HA revealed a clear diversification of seasonal from vaccine strain lineages. H3N2 seasonal clusters were closely related to the WHO recommended vaccine strains in each season. Most H1N1 isolates could be differentiated into 3 lineages. The A/Brisbane/59/2007 lineage, a vaccine strain for H1N1 since 2008, is closely related with the H1N1 subtypes circulating in 2009. HA sequences were conserved at the receptor-binding site. Amino acid variations in the antigenic site resulted in a possible N-linked glycosylation motif. Recent H3N2 isolates had higher genetic variations compared to H1N1 isolates. Most substitutions in the NP protein were clustered in the T-cell recognition domains.In this study we performed evolutionary genetic analysis of influenza A viruses in Thailand between 2006-2009. Although the current vaccine strain is efficient for controlling the circulating outbreak subtypes, surveillance is necessary to provide unambiguous information on emergent viruses. In summary, the findings of this study contribute the understanding of evolution in influenza A viruses in humans and is useful for routine surveillance and vaccine strain selection

Genome signatures in amino acid residues of human pandemic H1N1 in Thailand during 2009–2011 in gene; A) PB2, B) PB1, C) PA, D) HA, E) NP, F) NA, G) M1, H) M2 and I) NS.

<p>The graphical presentation was constructed using WebLogo. The height of symbol indicates the relative frequency of the corresponding amino acid at that position. Residue positions are given based on the nucleotide positions of each gene.</p

Whole Genome Characterization, Phylogenetic and Genome Signature Analysis of Human Pandemic H1N1 Virus in Thailand, 2009–2012

<div><h3>Background</h3><p>Three waves of human pandemic influenza occurred in Thailand in 2009–2012. The genome signature features and evolution of pH1N1 need to be characterized to elucidate the aspects responsible for the multiple waves of pandemic.</p> <h3>Methodology/Findings</h3><p>Forty whole genome sequences and 584 partial sequences of pH1N1 circulating in Thailand, divided into 1^st, 2^nd and 3^rd wave and post-pandemic were characterized and 77 genome signatures were analyzed. Phylogenetic trees of concatenated whole genome and HA gene sequences were constructed calculating substitution rate and d_N/d_S of each gene. Phylogenetic analysis showed a distinct pattern of pH1N1 circulation in Thailand, with the first two isolates from May, 2009 belonging to clade 5 while clades 5, 6 and 7 co-circulated during the first wave of pH1N1 pandemic in Thailand. Clade 8 predominated during the second wave and different proportions of the pH1N1 viruses circulating during the third wave and post pandemic period belonged to clades 8, 11.1 and 11.2. The mutation analysis of pH1N1 revealed many adaptive mutations which have become the signature of each clade and may be responsible for the multiple pandemic waves in Thailand, especially with regard to clades 11.1 and 11.2 as evidenced with V731I, G154D of PB1 gene, PA I330V, HA A214T S160G and S202T. The substitution rate of pH1N1 in Thailand ranged from 2.53×10⁻³±0.02 (M2 genes) to 5.27×10⁻³±0.03 per site per year (NA gene).</p> <h3>Conclusions</h3><p>All results suggested that this virus is still adaptive, maybe to evade the host's immune response and tends to remain in the human host although the d_N/d_S were under purifying selection in all 8 genes. Due to the gradual evolution of pH1N1 in Thailand, continuous monitoring is essential for evaluation and surveillance to be prepared for and able to control future influenza activities.</p> </div

Details of patients and pH1N1 influenza virus isolated in Thailand from May 2009 to April 2012.

**<p>Mild = Out patient, Moderate-In patient or admitted cases. Severe = Patient who treated in intensive care unit.</p

Phylogenetic tree of the HA gene of pH1N1 influenza viruses circulating in Thailand during 2009–2012.

<p>Phylogenetic tree of the HA gene of pH1N1 influenza viruses circulating in Thailand during 2009–2012.</p