Are passerine birds reservoirs for avian influenza viruses?

Although peridomestic passerines have been involved in influenza A virus (IAV) outbreaks in poultry, there is little evidence indicating they serve as reservoirs for these viruses under natural conditions. Recent molecular-based detections in passerines have challenged this paradigm, suggesting additional research is warranted to define the role of these birds as IAV hosts. To address this, we reviewed the published literature reporting results from IAV surveillance of passerines and conducted prospective virologic and serologic surveillance of passerines for IAVs. Passerines were collected and tested from 102 terrestrial wild bird species from Georgia, New Jersey, Delaware, and Minnesota. IAV antibodies were detected in 4/3,868 serum samples (0.1%), all from Minnesota. No virus was detected in 900 swab samples by virus isolation or matrix real-time reverse transcriptase polymerase chain reaction. Data from this study demonstrates that passerines have a limited role in IAV natural history and should not be considered reservoirs.