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A Meta‐Analysis of the Prevalence of Influenza A H5N1 and H7N9 Infection in Birds
Author(s) -
Bui C.,
Rahman B.,
Heywood A. E.,
MacIntyre C. R.
Publication year - 2017
Publication title -
transboundary and emerging diseases
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.392
H-Index - 63
eISSN - 1865-1682
pISSN - 1865-1674
DOI - 10.1111/tbed.12466
Subject(s) - influenza a virus subtype h5n1 , logistic regression , outbreak , veterinary medicine , prevalence , biology , transmission (telecommunications) , meta analysis , bird flu , epidemiology , demography , medicine , virology , virus , sociology , electrical engineering , engineering
Summary Despite a much higher rate of human influenza A ( H 7 N 9) infection compared to influenza A ( H 5 N 1), and the assumption that birds are the source of human infection, detection rates of H 7 N 9 in birds are lower than those of H 5 N 1. This raises a question about the role of birds in the spread and transmission of H 7 N 9 to humans. We conducted a meta‐analysis of overall prevalence of H 5 N 1 and H 7 N 9 in different bird populations (domestic poultry, wild birds) and different environments (live bird markets, commercial poultry farms, wild habitats). The electronic database, S copus, was searched for published papers, and G oogle was searched for country surveillance reports. A random effect meta‐analysis model was used to produce pooled estimates of the prevalence of H 5 N 1 and H 7 N 9 for various subcategories. A random effects logistic regression model was used to compare prevalence rates between H 5 N 1 and H 7 N 9. Both viruses have low prevalence across all bird populations. Significant differences in prevalence rates were observed in domestic birds, farm settings, for pathogen and antibody testing, and during routine surveillance. Random effects logistic regression analyses show that among domestic birds, the prevalence of H 5 N 1 is 47.48 (95% CI : 17.15–133.13, P < 0.001) times higher than H 7 N 9. In routine surveillance (where surveillance was not conducted in response to human infections or bird outbreaks), the prevalence of H 5 N 1 is still higher than H 7 N 9 with an OR of 43.02 (95% CI : 16.60–111.53, P < 0.001). H7N9 in humans has occurred at a rate approximately four times higher than H 5 N 1, and for both infections, birds are postulated to be the source. Much lower rates of H 7 N 9 in birds compared to H 5 N 1 raise doubts about birds as the sole source of high rates of human H 7 N 9 infection. Other sources of transmission of H 7 N 9 need to be considered and explored.