Phylogeography and evolutionary history of reassortant H9N2 viruses with potential human health implications.

Avian influenza viruses of the H9N2 subtype have seriously affected the poultry industry of the Far and Middle East since the mid-1990s and are considered one of the most likely candidates to cause a new influenza pandemic in humans. To understand the genesis and epidemiology of these viruses, we investigated the spatial and evolutionary dynamics of complete genome sequences of H9N2 viruses circulating in nine Middle Eastern and Central Asian countries from 1998 to 2010. We identified four distinct and cocirculating groups (A, B, C, and D), each of which has undergone widespread inter- and intrasubtype reassortments, leading to the generation of viruses with unknown biological properties. Our analysis also suggested that eastern Asia served as the major source for H9N2 gene segments in the Middle East and Central Asia and that in this geographic region within-country evolution played a more important role in shaping viral genetic diversity than migration between countries. The genetic variability identified among the H9N2 viruses was associated with specific amino acid substitutions that are believed to result in increased transmissibility in mammals, as well as resistance to antiviral drugs. Our study highlights the need to constantly monitor the evolution of H9N2 viruses in poultry to better understand the potential risk to human health posed by these viruses.

Epidemic outbreaks, diagnostics, and control measures of the H5N1 highly pathogenic avian influenza in the Kingdom of Saudi Arabia, 2007-08.

The first outbreak of H5N1 highly pathogenic avian influenza (HPAI) in the Kingdom of Saudi Arabia (KSA) occurred in two "backyard" flocks of Houbara bustards and falcons in February 2007. Subsequent outbreaks were seen through the end of 2007 in "backyard" birds including native chickens, ostriches, turkeys, ducks, and peacocks. From November 2007 through January 2008, H5N1 HPAI outbreaks occurred in 19 commercial poultry premises, including two broiler breeder farms, one layer breeder farm, one ostrich farm, and 15 commercial layer farms, with approximately 4.75 million birds affected. Laboratory diagnosis of all H5N1-positive cases was conducted at the Central Veterinary Diagnostic Laboratory (CVDL) in Riyadh, Saudi Arabia. A combination of diagnostic tests was used to confirm the laboratory diagnosis. A rapid antigen-capture test and real-time reverse transcriptase-PCR (rtRT-PCR) assay on clinical and field specimens were conducted initially. Meanwhile, virus isolation in specific-pathogen-free embryonating chicken eggs was performed and was followed by hemagglutinin (HA) and hemagglutination inhibition tests, then rapid antigen-capture and rtRT-PCR tests on HA-positive allantoic fluid samples. In most HPAI cases, a complete laboratory diagnosis was made within 24-48 hr at the CVDL. Saudi Arabian government officials made immediate decisions to depopulate all H5N1-affected and nonaffected flocks within a 5-km radius area and applied quarantine zones to prevent the virus from spreading to other areas. Other control measures, such as closure of live bird markets and intensive surveillance tests on all poultry species within quarantine zones, were in place during the outbreaks. As a result, the HPAI outbreaks were quickly controlled, and no positive cases were detected after January 29, 2008. The KSA was declared free of HPAI on April 30, 2008, by the World Animal Health Organization.

Co-circulation of two sublineages of HPAI H5N1 virus in the Kingdom of Saudi Arabia with unique molecular signatures suggesting separate introductions into the commercial poultry and falconry sectors.

Since early 2007, the Kingdom of Saudi Arabia (KSA) has experienced several highly pathogenic avian influenza (HPAI) H5N1 outbreaks in the falconry and poultry sectors. The public health threat associated with peculiar husbandry systems, requiring close contact between humans and birds of prey, highlights the need of an improved understanding of the epidemiology and of the viral characteristics of H5N1 viruses circulating in the region. Here we report molecular and phylogenetic analyses of H5N1 viruses isolated in the KSA in 2007 in distinct compartments of avian husbandry. From the results of our investigation it appears that two separate introductions into the different sectors occurred. The identification of specific amino acid mutations, which are described as genetic signatures of human influenza A viruses or known to confer resistance to antiviral drugs, raises concerns for the possible human health implications of the KSA H5N1 viruses.