If we don’t know all the sequences, how can they be so sure that the U.S. LPAI is not HPAI?
1 Testing for the presence of avian influenza (AI) requires that samples be taken from live birds, dead birds or the environment birds inhabit. The Departments of Agriculture and Interior are working collaboratively with States and academic institutions to sample wild birds throughout the United States for the presence of highly pathogenic avian influenza. The interagency plan outlines five specific strategies for early detection of the virus in wild migratory birds, including: investigation of disease-outbreak events in wild birds; expanded monitoring of apparently healthy live wild birds; monitoring of hunter-killed birds; use of sentinel animals; and environmental sampling of bird feces. 2 A series of AI rapid screening tests are performed that cannot differentiate between highly pathogenic AI (HPAI) and low pathogenic AI (LPAI) viruses. The initial rapid screening tests are highly sensitive and can detect active and inactive viruses in samples. Because these rapid screening tests are highly sensitive, it is not uncommon to have positive results for a specific subtype on the initial screen test and yet not be able to isolate a virus of that subtype.
3 This test involves identifying the genetic sequence or key parts of the sequence, of the virus grown and comparing it to known AI genetic sequences. These known sequences, such as that of the highly pathogenic H5N1 AI virus circulating overseas, are stored in databanks. If the genetic sequence matches that of a known highly pathogenic AI virus, the sample is considered to be highly pathogenic.