Highly pathogenic avian influenza virus subtype H5N1 in Africa: a comprehensive phylogenetic analysis and molecular characterization of isolates.
Highly pathogenic avian influenza virus A/H5N1 was first officially reported in Africa in early 2006. Since the first outbreak in Nigeria, this virus spread rapidly to other African countries. From its emergence to early 2008, 11 African countries experienced A/H5N1 outbreaks in poultry and human cases were also reported in three of these countries. At present, little is known of the epidemiology and molecular evolution of A/H5N1 viruses in Africa. We have generated 494 full gene sequences from 67 African isolates and applied molecular analysis tools to a total of 1,152 A/H5N1 sequences obtained from viruses isolated in Africa, Europe and the Middle East between 2006 and early 2008. Detailed phylogenetic analyses of the 8 gene viral segments confirmed that 3 distinct sublineages were introduced, which have persisted and spread across the continent over this 2-year period. Additionally, our molecular epidemiological studies highlighted the association between genetic clustering and area of origin in a majority of cases. Molecular signatures unique to strains isolated in selected areas also gave us a clearer picture of the spread of A/H5N1 viruses across the continent. Mutations described as typical of human influenza viruses in the genes coding for internal proteins or associated with host adaptation and increased resistance to antiviral drugs have also been detected in the genes coding for transmembrane proteins. These findings raise concern for the possible human health risk presented by viruses with these genetic properties and highlight the need for increased efforts to monitor the evolution of A/H5N1 viruses across the African continent. They further stress how imperative it is to implement sustainable control strategies to improve animal and public health at a global level.
Cattoli
Giovanni
G
OIE/FAO Reference Laboratory for avian influenza and Newcastle disease, Istituto Zooprofilattico Sper.le delle Venezie, Legnaro, PD, Italy.
Monne
Isabella
I
Fusaro
Alice
A
Joannis
Tony M
TM
Lombin
Lami H
LH
Aly
Mona M
MM
Arafa
Abdel S
AS
Sturm-Ramirez
Katharine M
KM
Couacy-Hymann
Emmanuel
E
Awuni
Joseph A
JA
Batawui
Komla B
KB
Awoume
Kodzo A
KA
Aplogan
Gilbert L
GL
Sow
Adama
A
Ngangnou
Andrè C
AC
El Nasri Hamza
Iman M
IM
Gamatié
Djibo
D
Dauphin
Gwenaelle
G
Domenech
Joseph M
JM
Capua
Ilaria
I
D000349:Africa; D001499:Bayes Theorem; D019143:Evolution, Molecular; D053124:Influenza A Virus, H5N1 Subtype / Q000145:classification* / Q000235:genetics / Q000472:pathogenicity; D009154:Mutation; D010802:Phylogeny