Abstract
When the A(H1N1)pdm09 pandemic influenza virus moved into the post-pandemic period, there was a worldwide predominance of the seasonal influenza A(H3N2) and B viruses. However, A(H1N1)pdm09 became the prevailing subtype in the 2011–2012 influenza season in Mexico and most of Central America. During this season, we collected nasopharyngeal swabs of individuals presenting with influenza-like illness at our institution in Mexico City. Samples were tested for seasonal A(H3N2) and B influenza viruses, as well as A(H1N1)pdm09 by real-time reverse transcription–polymerase chain reaction. Of 205 samples tested, 46% were positive to influenza, all of them A(H1N1)pdm09. The clinical characteristics of patients showed a similar pattern to the 2009 pandemic cases. Using next generation sequencing, we obtained whole genome sequences of viruses from 4 different patients, and in 8 additional viruses we performed partial Sanger sequencing of the HA segment. Non-synonymous changes found in the Mexican isolates with respect to the prototype isolate H1N1 (A/California/04/2009) included HA S69T, K163R and N260D unique to 2012 Mexican and North American isolates and located within or adjacent to HA antigenic sites; HA S143G, S185T, A197T and S203T previously reported in viruses from the 2010–2011 season, located within or adjacent to HA antigenic sites; and HA E374K located in a relevant site for membrane fusion. All Mexican isolates had an oseltamivir-sensitive genotype. Phylogenetic analysis with all 8 influenza gene segments showed that 2012 Mexican sequences formed a robust, distinct cluster. In all cases, 2012 Mexican sequences tended to group with 2010–2011 Asian and European sequences, but not with 2009 Mexican sequences, suggesting a possible recent common ancestor between these latter regions and the 2012 Mexican viruses. It remains to be defined if these viral changes represent an important antigenic drift that would enable viral immune evasion and/or affect influenza vaccine effectiveness.
Highlights
The pandemic A(H1N1)pdm09 influenza virus was originally detected in Mexico and the United States in March 2009 [1]
Clinical characteristics of the patients Between October 4 and December 23, 2011, nasopharyngeal swabs from 90 patients with influenza-like illness (ILI) were obtained and all tested negative for influenza viruses
Following the post-pandemic period initiation in August 2010, predominance of the A(H1N1)pdm09 virus was observed for the first time in the 2011–2012 influenza season in Mexico and most countries of Central America
Summary
The pandemic A(H1N1)pdm influenza virus was originally detected in Mexico and the United States in March 2009 [1]. During the 2011–2012 influenza season in the United States, the aforementioned influenza viruses were still circulating but the predominant subtype was A(H3); in Mexico, a contrasting predominance of the A(H1N1)pdm virus was observed, with very limited circulation of influenza viruses A(H3) and B [3,4]. This A(H1N1)pdm virus predominance during the 2011–2012 influenza season was observed in Guatemala, Honduras, El Salvador, Nicaragua, Costa Rica and Panama [3]. Distinctive patterns of the 2011–2012 influenza season were observed within North and Central America, with predominance of the A(H3) subtype and B lineage in the United States and Canada, respectively, and a predominance of the A(H1N1)pdm subtype in Mexico and most of Central America
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
