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Research Project: Intervention Strategies to Prevent and Control Disease Outbreaks Caused by Emerging Strains of Avian Influenza Viruses

Location: Exotic & Emerging Avian Viral Diseases Research

Title: Agricultural and geographic factors shaped the 2015 highly pathogenic avian influenza H5N2 outbreak within the midwestern United States poultry industries

item HICKS, JOSEPH - University Of Georgia
item DUVUURI, VENKATA - University Of Georgia
item LEE, DONG-HUN - University Of Connecticut
item TORCHETTI, MIA KIM - Animal And Plant Health Inspection Service (APHIS)
item Swayne, David
item BAHL, JUSTIN - University Of Georgia

Submitted to: PLoS Pathogens
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/15/2020
Publication Date: 1/20/2020
Citation: Hicks, J.T., Duvuuri, V.R., Lee, D., Torchetti, M., Swayne, D.E., Bahl, J. 2020. Agricultural and geographic factors shaped the 2015 highly pathogenic avian influenza H5N2 outbreak within the midwestern United States poultry industries. PLoS Pathogens. 16(1):e1007857.

Interpretive Summary: The highly pathogenic avian influenza outbreak among poultry farms in the midwestern United States appears to be influenced by agricultural and geographic factors. After initial introduction of the virus into the poultry industries, no further introductions (such as from a wild bird reservoir or long-distance movement) were necessary to explain the continuation of the outbreak from March to June 2015. Additionally, evidence suggests that proximity of farms increases the chances of viral movement between two locations. While many theories have been proposed to explain the transmission of virus among poultry farms, the support for road density as an important driver of viral movement in our model suggests human-based transportation plays a key role.

Technical Abstract: The 2014 – 2015 highly pathogenic avian influenza (HPAI) H5NX outbreak represents the largest and most expensive HPAI outbreak in the United States, to date. Despite extensive traditional and molecular epidemiological studies, factors associated with the spread of HPAI among midwestern poultry premises remain unclear. To better understand the dynamics of this portion of the outbreak, 182 full genome HPAI H5N2 sequences isolated from commercial layer chicken and turkey production premises were analyzed using evolutionary models modified to incorporate epidemiological and geographic information. Epidemiological compartmental models constructed in a phylogenetic framework provided evidence that poultry production type acted as a barrier to the transmission of virus among midwestern poultry farms. Furthermore, after initial introduction, a continuous external source of virus was not needed to explain the propagation of HPAI cases within the commercial poultry industries. Discrete trait diffusion models indicated that within state viral transitions occurred more frequently than inter-state transitions. Distance, road density and proportion of water coverage were all supported as associated with viral transition between county groups (Bayes Factor > 3.0). Together these findings indicate that the midwestern poultry industries was not a single homogenous population, but rather, the outbreak was shaped by poultry industries and geographic factors.