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Abstract  Our aim was to establish the phylogenetic and genetic relationships among avian influenza viruses (AIV) recently isolated from poultry in Israel. During this study we analyzed complete nucleotide sequences of two envelope (hemagglutinin and neuraminidase) and six internal genes (polymerase B1, polymerase B2, polymerase A, nucleoprotein, nonstructural, and matrix) of 29 selected H9N2 and six internal genes of five H5N1 viruses isolated in Israel during 2000–2006. Comparative genetic and phylogenetic analyses of these sequences revealed that the local H5N1 viruses are closely related to H5N1 viruses isolated in European, Asian, and Middle Eastern countries in 2005–2006. The H9N2 Israeli isolates, together with viruses isolated in Jordan and Saudi Arabia formed a single group. Our data support the claim that during recent years a new endemic focus of H9N2 has been formed in the Middle East. The introduction of H5N1 and co-circulation of these two subtypes of AIV in this region may augment the risk of potentially pandemic strains emergence. [ABSTRACT FROM AUTHOR]

Abstract  The biological diversity within viruses is one of the largest found in all other forms of nature. Many mechanisms contribute to virus diversity and include incorporating genetic material from the host, recombination between viruses belonging to the same or to a different family, and even recombination between viruses normally infecting different hosts. In particular, avian viruses can utilize all three of these mechanisms to generate new viruses. It is well documented that recombinations can occur between Marek’s disease virus (MDV), an oncogenic herpesvirus, fowlpox virus (FPV), and various avian retroviruses. In addition, chicken infectious anemia virus (CIAV), a circovirus, was created by several inter-family recombination events, which occurred between plant and animal viruses. The circovirus represents the ancestral creation of a recombination between a plant DNA virus (nanovirus) and a mammalian RNA virus (calicivirus), through a transition of RNA to DNA made by an endogenous mammalian retrovirus. The present review will discuss the current knowledge on recombination events that have occurred between avian herpesviruses and retroviruses following dual infections in vitro and in vivo. In addition, we will discuss recombinations between fowlpox viruses and the avian retrovirus reticuloendotheliosis (REV). Finally, the review will address the creation of CIAV and how it evolved from recombinations between a plant virus and an animal virus. [ABSTRACT FROM AUTHOR]