Multiple introductions of highly pathogenic avian influenza H5N1 viruses into Bangladesh

Abstract

Highly pathogenic H5N1 and low pathogenic H9N2 influenza viruses are endemic to poultry markets in Bangladesh and have cocirculated since 2008. H9N2 influenza viruses circulated constantly in the poultry markets, whereas highly pathogenic H5N1 viruses occurred sporadically, with peaks of activity in cooler months. Thirty highly pathogenic H5N1 influenza viruses isolated from poultry were characterized by antigenic, molecular, and phylogenetic analyses. Highly pathogenic H5N1 influenza viruses from clades 2.2.2 and 2.3.2.1 were isolated from live bird markets only. Phylogenetic analysis of the 30 H5N1 isolates revealed multiple introductions of H5N1 influenza viruses in Bangladesh. There was no reassortment between the local H9N2 influenza viruses and H5N1 genotype, despite their prolonged cocirculation. However, we detected two reassortant H5N1 viruses, carrying the M gene from the Chinese H9N2 lineage, which briefly circulated in the Bangladesh poultry markets and then disappeared. On the other hand, interclade reassortment occurred within H5N1 lineages and played a role in the genesis of the currently dominant H5N1 viruses in Bangladesh. Few ‘human-like' mutations in H5N1 may account for the limited number of human cases. Antigenically, clade 2.3.2.1 H5N1 viruses in Bangladesh have evolved since their introduction and are currently mainly homogenous, and show evidence of recent antigenic drift. Although reassortants containing H9N2 genes were detected in live poultry markets in Bangladesh, these reassortants failed to supplant the dominant H5N1 lineage.

The Continuing Evolution of H5N1 and H9N2 Influenza Viruses in Bangladesh Between 2013 and 2014

“…All virus isolates were definitively subtyped by endpoint RT-PCR and sequencing. Viral RNA extraction and nucleotide sequencing were performed as previously described (14, 12). Three of the HPAI H5N1 virus cultures that were co-infected with low-pathogenic H9N2 viruses, were treated with anti-H9N2 chicken antiserum to allow full genome sequencing of the H5N1 virus.…”

“…Clade 2.3.4.2 was detected in March 2011 in Eastern Bangladesh and was successfully eradicated after the outbreak was stamped out. Clade 2.3.2.1a, first detected in January 2011, then completely replaced the previously predominant clade 2.2.2 (12). It has caused 4 human cases (21), one of which was fatal (10).…”

Highly Pathogenic Reassortant Avian Influenza A(H5N1) Virus Clade 2.3.2.1a in Poultry, Bhutan

“…In India and Bangladesh, highly pathogenic avian influenza (HPAI) A(H5N1) viruses of the 2.3.2.1a genetic lineage have circulated in poultry since 2011 ( 1 – 3 ). Subtype H5N1 endemicity is complicated by co-circulating subtype H9N2, G1_Mideast lineage ( 4 , 5 ), which derives 5 internal genes from HPAI A(H7N3) virus from Pakistan ( 4 ).…”

Emerging and re-emerging infectious disease threats in South Asia: status, vulnerability, preparedness, and outlook

“…[16][17][18] Rates of neuroleptospirosis and leptospirosis have been rising in north India and Sri Lanka and have been associated with disseminated intravascular coagulation. 19 20 The growing proportion of severe cases of leptospirosis has created massive pressures on the healthcare delivery systems in affected countries.…”