Frequency of D222G haemagglutinin mutant of pandemic (H1N1) pdm09 influenza virus in Tunisia between 2009 and 2011

BACKGROUND: The novel pandemic A (H1N1) pdm09 virus was first identified in Mexico in April 2009 and since then it spread worldwide over a short period of time. Although the virus infection is generally associated with mild disease and a relatively low mortality, it is projected that mutations in specific regions of the viral genome, especially within the receptor binding domain of the haemagglutinin (HA) protein could result in more virulent virus stains, leading to a more severe pathogenicity. METHODS: To monitor the genetic polymorphisms at position 222 of Haemagglutinin of influenza A(H1N1)pdm09 viruses from both outpatients with mild influenza and individuals with severe disease requiring hospitalization, during 2009-2010 and 2010-2011 seasons, a sequence-based genotypic assessment of viral populations to understand the prevalence of D222G mutation. RESULTS: The D222G was identified in clinical specimens from 3 out of 42 cases analyzed in Tunisia with severe outcome (7%). Interestingly, in one fatal case out of four viruses taken from fatal cases studied (25%). Also this mutation was found in one mild case out of 8 mild cases studied (0.1%). D222E substitution was found in virus taken from one patient with severe clinical syndrome (2%) out of 42 severe cases analyzed and E374K substitution was found in two severe cases (4%) out of 42 severe cases studied. CONCLUSIONS: A specific mutation in the viral haemagglutinin (D222G) was found in fatal, severe and mild case. Further virological, clinical and epidemiological investigations are needed to ascertain the role of this and other mutations that may alter the virulence and transmissibility of the pandemic influenza A (H1N1)pdm09. VIRTUAL SLIDES: The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/1027334947811255.S

Virological Surveillance of Influenza Viruses during the 2008-09, 2009-10 and 2010-11 Seasons in Tunisia

BACKGROUND: The data contribute to a better understanding of the circulation of influenza viruses especially in North-Africa. OBJECTIVE: The objective of this surveillance was to detect severe influenza cases, identify their epidemiological and virological characteristics and assess their impact on the healthcare system. METHOD: We describe in this report the findings of laboratory-based surveillance of human cases of influenza virus and other respiratory viruses' infection during three seasons in Tunisia. RESULTS: The 2008-09 winter influenza season is underway in Tunisia, with co-circulation of influenza A/H3N2 (56.25%), influenza A(H1N1) (32.5%), and a few sporadic influenza B viruses (11.25%). In 2010-11 season the circulating strains are predominantly the 2009 pandemic influenza A(H1N1)pdm09 (70%) and influenza B viruses (22%). And sporadic viruses were sub-typed as A/H3N2 and unsubtyped influenza A, 5% and 3%, respectively. Unlike other countries, highest prevalence of influenza B virus Yamagata-like lineage has been reported in Tunisia (76%) localised into the clade B/Bangladesh/3333/2007. In the pandemic year, influenza A(H1N1)pdm09 predominated over other influenza viruses (95%). Amino acid changes D222G and D222E were detected in the HA gene of A(H1N1)pdm09 virus in two severe cases, one fatal case and one mild case out of 50 influenza A(H1N1)pdm09 viruses studied. The most frequently reported respiratory virus other than influenza in three seasons was RSV (45.29%). CONCLUSION: This article summarises the surveillance and epidemiology of influenza viruses and other respiratory viruses, showing how rapid improvements in influenza surveillance were feasible by connecting the existing structure in the health care system for patient records to electronic surveillance system for reporting ILI cases.This research was supported by Unit Virology, Microbiology Laboratory Charles Nicolle's Hospital as National Influenza Centre-Tunis and Influenza and Respiratory Laboratory, Instituto de Salud Carlos III as National Influenza Centre-Madrid. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. It is just an informal statement of the study and the members of the ethic committee of Charles Nicolle's hospital have previously always approved the work of the NICS

Genetic diversity of HA1 domain of heammaglutinin gene of influenza A(H1N1)pdm09 in Tunisia

We present major results concerning isolation and determination of the nucleotide sequence of hemagglutinin (HA1) of the pandemic (H1N1)pdm09 influenza viruses found in Tunisia. Amino acid analysis revealed minor amino acid changes in the antigenic or receptor-binding domains. We found mutations that were also present in 1918 pandemic virus, which includes S183P in 4 and S185T mutation in 19 of 27 viruses analyzed from 2011, while none of the 2009 viruses carried these mutations. Also two specific amino acid differences into N-glycosylation sites (N288T and N276H) were detected. The phylogenetic analysis revealed that the majority of the Tunisian isolates clustered with clade A/St. Petersburg/27/2011 viruses characterized by D97N and S185T mutations. However it also reveals a trend of 2010 strains to accumulate amino acid variation and form new phylogenetic clade with three specific amino acid substitutions: V47I, E172K and K308E.We are grateful to the World Health Organization office in Tunis for the financial help in order to publish our work.S

Percentage of consultant in sentinel centre during 2009–2010 and 2010–2011.

<p>Percentage of consultant in sentinel centre during 2009–2010 and 2010–2011.</p

Phylogenetic relationship of partial length HA sequences of influenza A(H1N1)pdm09 viruses from fatal, severe and mild cases in Tunisia during 2009–2010/2010–2011 seasons.

<p>Fatal case#; case in care unit+; severe case *; mild case-. The tree was rooted with the vaccine strain A/California/07/2009 (boxed) as outgroup. Branch lengths are drawn to scale. Signature amino acid changes (H1 numbering) are annotated at the nodes of each cluster. Viruses with 222G or 222E changes are marked in the tree.</p

Map of ILI sites and population covered by ILI sites in different Tunisian governorates in 2009–2010 season.

<p>Map of ILI sites and population covered by ILI sites in different Tunisian governorates in 2009–2010 season.</p

Sentinel data of percentage of specimens positive for influenza in comparison with influenza A(H1N1)pdm09_season 2008–2009, 2009–2010 and 2010–2011.

<p>Sentinel data of percentage of specimens positive for influenza in comparison with influenza A(H1N1)pdm09_season 2008–2009, 2009–2010 and 2010–2011.</p

Phylogenetic comparison of partial length HA sequences of influenza B (Yamagata and Victoria-lineage) from severe and mild cases in Tunisia during 2009–2010 and 2010–2011 seasons.

<p>Phylogenetic comparison of partial length HA sequences of influenza B (Yamagata and Victoria-lineage) from severe and mild cases in Tunisia during 2009–2010 and 2010–2011 seasons.</p