Wild bird surveillance for avian influenza virus

First detection of influenza A virus genes from wild raccoons in Japan

Serological surveys have shown that wild raccoons are exposed to influenza A viruses (IAVs); however, no genetic evidence for this IAV infection has been found. In the present study, we first detected IAV genes in wild raccoons captured during periods other than the wintering season of migratory waterfowl and epidemic season of influenza in Japan. Viral matrix (M) and nucleoprotein (NP) genes were detected by a conventional reverse transcription-polymerase chain reaction assay from three suckling siblings and one juvenile without any noticeable clinical signs, although the NP gene could not be detected from one sibling. The sequences of M gene fragments detected from the rectal swabs of three suckling siblings were comparable with each other but different from those detected from the nasal swab of the juvenile raccoon caught from a different site. The sequences of NP gene fragments detected from two suckling siblings were also comparable. These genetic evidences suggest that IAV is maintained among raccoon populations in the northern part of Japan. Further genetic and virological investigation of IAV infection in wild raccoons is needed to better understand the IAV ecology in the field.

The pandemic potential of avian influenza A(H7N9) virus: a review

In March 2013 the first cases of human avian influenza A(H7N9) were reported to the World Health Organization. Since that time, over 650 cases have been reported. Infections are associated with considerable morbidity and mortality, particularly within certain demographic groups. This rapid increase in cases over a brief time period is alarming and has raised concerns about the pandemic potential of the H7N9 virus. Three major factors influence the pandemic potential of an influenza virus: (1) its ability to cause human disease, (2) the immunity of the population to the virus, and (3) the transmission potential of the virus. This paper reviews what is currently known about each of these factors with respect to avian influenza A(H7N9). Currently, sustained human-to-human transmission of H7N9 has not been reported; however, population immunity to the virus is considered very low, and the virus has significant ability to cause human disease. Several statistical and geographical modelling studies have estimated and predicted the spread of the H7N9 virus in humans and avian species, and some have identified potential risk factors associated with disease transmission. Additionally, assessment tools have been developed to evaluate the pandemic potential of H7N9 and other influenza viruses. These tools could also hypothetically be used to monitor changes in the pandemic potential of a particular virus over time.

Large-scale avian influenza surveillance in wild birds throughout the United States

Avian influenza is a viral disease that primarily infects wild and domestic birds, but it also can be transmitted to a variety of mammals. In 2006, the United States of America Departments of Agriculture and Interior designed a large-scale, interagency surveillance effort that sought to determine if highly pathogenic avian influenza viruses were present in wild bird populations within the United States of America. This program, combined with the Canadian and Mexican surveillance programs, represented the largest, coordinated wildlife disease surveillance program ever implemented. Here we analyze data from 197,885 samples that were collected from over 200 wild bird species. While the initial motivation for surveillance focused on highly pathogenic avian influenza, the scale of the data provided unprecedented information on the ecology of avian influenza viruses in the United States, avian influenza virus host associations, and avian influenza prevalence in wild birds over time. Ultimately, significant advances in our knowledge of avian influenza will depend on both large-scale surveillance efforts and on focused research studies.