Identification of the agent: Suspensions in antibiotic solution of oropharyngeal and cloacal swabs
(or faeces) taken from live birds, or of faeces and pooled samples of organs from dead birds, are
inoculated into the allantoic cavity of 9- to 11-day-old embryonated chicken eggs. The eggs are
incubated at 37°C (range 35–39°C) for 2–7 days. The allantoic fluid of any eggs containing dead or
dying embryos during the incubation and all eggs at the end of the incubation period are tested for
the presence of haemagglutinating activity. The presence of influenza A virus can be confirmed by
an immunodiffusion test between concentrated virus and an antiserum to the nucleocapsid and/or
matrix antigens, both of which are common to all influenza A viruses, or by real-time reversetranscription
polymerase chain reaction (RT-PCR) on the allantoic fluids. Isolation in embryos has
recently been replaced under certain circumstances by direct detection in samples, of one or more
segments of the influenza A genome using real-time RT-PCR or other validated molecular
techniques.