00000ctm a22000003a 4500 UP-1685523046126267735 Buklod 20140213154341.0 m o j ta 140213s2011 xx d r |||| u| (iLib)UPMNL-00013079030 UPM-CPH eng LG995 2011 P93 O72 Orbina, Jun Ryan C. Hemagglutinin gene mutation profiling and oseltamivir resistance genotyping of pandemic (H1N1) 2009 influenza viruses among human cases in Baguio City, Philippines Jun Ryan C. Orbina. 2011 112 leaves Thesis (MS Public Health, Medical Microbiology)--University of the Philippines Manila The Pandemic Influenza A (H1N1) 2009 virus had caused the global public health concern after its emergence in April 2009. On August 2010, when the post-pandemic phase was declared by the World Health Organization (WHO), the virus had already affected 214 countries and territories, including the Philippines. In the post-pandemic phase, the detection of antigenic or genetic changes and the appearance of antiviral resistance in the circulating viruses are among the surveillance objectives recommended by the WHO. Recognizing the need, this study was done to describe the proportions and determine the spatial and temporal patterns of emergence of Hemagglutinin (HA) gene mutations and oseltamivir resistance in Influenza Pandemic (H1N1) 2009 virus among human cases in Baguio City, Philippines from April 2009 to December 2010. Nucleotide sequencing and phylogenetic analysis of the HA gene and detection of the H275Y marker in the NA gene by Polymerase Chain Reaction-Restriction Fragment Length Polymorphism were done on the viruses. HA substitutions D239G/N/E/Y, most commonly-implicated in severe infections by other studies, were not detected among the 125 analyzed samples. E391K/Y/D substitutions occurred in 35.48% of samples, with E391K co-segregating with D114N and N142D in the 2010 samples. A functionally-significant novel substitution, N142D, was detected in 20.97% of samples, and was maintained by recent collections. Four novel substitutions (i.e., P100S/Y/A, T214A, S220T and I338V) appeared in 100% of the samples analyzed. Phylogenetic analysis of the HA gene revealed that the samples are closely-related and there was strong bootstrap evidence to conclude a temporal or spatial pattern of emergence of substitutions. The oseltamivir-resistance marker H275Y was found as a mixed infection in one out of 149 samples analyzed (0.67%). This study is the first report of oseltamivir resistance in Pandemic (H1N1) 2009 in the Philippines. Furthermore, this study also highlighted the amino acid substitutions whioch were maintained by the viruses as they underwent antigenic drift. Influenza A Virus. Hemagglutinin. Microbial genetics. UP UPMNL CPH LG995 2011 P93 O72 Thesis