Various diagnostic techniques are available for the detection of influenza viruses although virus isolation remains the gold standard method for epidemiologic and genetic studies. RT-PCR is a useful tool for the detection of these viruses. This technique is important for rapid detection of influenza virus but one limitation is that it does not provide information on whether the virus is infectious or dead. This technique has the limitations of producing false negative as well as false positive results. This book, therefore, provides new information on the isolation of avian influenza virus from samples that were found to be AIV negative by real time RT-PCR screening. Wild birds are usually co-infected with influenza A viruses and other paramyxoviruses. One of the most important paramyxovirus that infects wild birds is avian paramyxovirus type 1 (APMV-1), also known as the Newcastle disease virus (NDV). This virus has the potential to outgrow AIV during virus isolation in eggs. As part of this study, a method was developed to inhibit NDV overgrowth in eggs by treating samples with anti-NDV antiserum before inoculation in embryonated chicken eggs.