As the avian influenza virus H5N1 swept from Asia across Russia to Europe, Nigeria was the first country in Africa to report the emergence of this highly pathogenic virus. Here we analyse H5N1 sequences in poultry from two different farms in Lagos state and find that three H5N1 lineages were independently introduced through routes that coincide with the flight paths of migratory birds, although independent trade imports cannot be excluded.

In Africa, highly pathogenic avian influenza H5N1 virus was first detected in northern Nigeria and later also in other regions of the country. Since then, seven other African countries have reported H5N1 infections. This study reports a comparison of full-length genomic sequences of H5N1 isolates from seven chicken farms in Nigeria and chicken and hooded vultures in Burkina Faso with earlier H5N1 outbreaks worldwide. In addition, the antigenicity of Nigerian H5N1 isolates was compared with earlier strains. All African strains clustered within three sublineages denominated A (south-west Nigeria, Niger), B (south-west Nigeria, Egypt, Djibouti) and C (northern Nigeria, Burkina Faso, Sudan, Côte d'Ivoire), with distinct nucleotide and amino acid signatures and distinct geographical distributions within Africa. Probable non-African ancestors within the west Asian/Russian/European lineage distinct from the south-east Asian lineages were identified for each sublineage. All reported human cases in Africa were caused by sublineage B. Substitution rates were calculated on the basis of sequences from 11 strains from a single farm in south-west Nigeria. As H5N1 emerged essentially at the same time in the north and south-west of Nigeria, the substitution rates confirmed that the virus probably did not spread from the north to the south, given the observed sequence diversity, but that it entered the country via three independent introductions. The strains from Burkina Faso seemed to originate from northern Nigeria. At least two of the sublineages also circulated in Europe in 2006 as seen in Germany, further suggesting that the sublineages had already emerged outside of Africa and seemed to have followed the east African/west Asian and Black Sea/Mediterranean flyways of migratory birds.

Drug repositioning has received increased attention since the past decade as several blockbuster drugs have come out of repositioning. Computational approaches are significantly contributing to these efforts, of which, network-based methods play a key role. Various structural (topological) network measures have thereby contributed to uncovering unintuitive functional relationships and repositioning candidates in drug-disease and other networks. This review gives a broad overview of the topic, and offers perspectives on the application of topological measures for network analysis. It also discusses unexplored measures, and draws attention to a wider scope of application efforts, especially in drug repositioning.

Genetic analysis of highly pathogenic avian influenza (H5N1) viruses from poultry and hooded vultures in Burkina Faso shows that these viruses belong to 1 of 3 sublineages initially found in Nigeria and later in other African countries. Hooded vultures could potentially be vectors or sentinels of influenza subtype H5N1, as are cats and swans elsewhere.

To investigate the presence and persistence of avian influenza virus in African birds, we monitored avian influenza in wild and domestic birds in two different regions in Nigeria. We found low-pathogenic avian influenza (LPAI) H5N2 viruses in three spur-winged geese (Plectropterus gambensis) in the Hadejia–Nguru wetlands. Phylogenetic analyses revealed that all of the genes, except the non-structural (NS) genes, of the LPAI H5N2 viruses were more closely related to genes recently found in wild and domestic birds in Europe. The NS genes formed a sister group to South African and Zambian NS genes. This suggested that the Nigerian LPAI H5N2 viruses found in wild birds were reassortants exhibiting an NS gene that circulated for at least 7 years in African birds and is part of the African influenza gene pool, and genes that were more recently introduced into Africa from Eurasia, most probably by intercontinental migratory birds. Interestingly the haemagglutinin and neuraminidase genes formed a sister branch to highly pathogenic avian influenza (HPAI) H5N2 strains found in the same wild bird species in the same wetland only 1 year earlier. However, they were not the closest known relatives of each other, suggesting that their presence in the wetland resulted from two separate introductions. The presence of LPAI H5N2 in wild birds in the Hadejia–Nguru wetlands, where wild birds and poultry occasionally mix, provides ample opportunity for infection across species boundaries, with the potential risk of generating HPAI viruses after extensive circulation in poultry.