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Regional Transmission and Reassortment of Highly Pathogenic Avian Influenza (HPAI) Viruses in Bulgarian Poultry 2017/18

Venkatesh, D; Brouwer, A; Goujgoulova, G; Ellis, R; Seekings, J; Brown, I; Lewis, N


D Venkatesh

A Brouwer

G Goujgoulova

R Ellis

J Seekings

I Brown

N Lewis


Between 2017 and 2018, several farms across Bulgaria reported outbreaks of H5 highly-pathogenic avian influenza (HPAI) viruses. In this study we used genomic and traditional epidemiological analyses to trace the origin and subsequent spread of these outbreaks within Bulgaria.
Both methods indicate two separate incursions, one restricted to the northeastern region of Dobrich, and another largely restricted to Central and Eastern Bulgaria including places such as Plovdiv,
Sliven and Stara Zagora, as well as one virus from the Western region of Vidin. Both outbreaks likely originate from di�erent European virus ancestors circulating in 2017. The viruses were likely introduced by wild birds or poultry trade links in 2017 and have continued to circulate, but due to lack of contemporaneous sampling and sequences from wild bird viruses in Bulgaria, the precise route and timing of introduction cannot be determined. Analysis of whole genomes indicates a complete lack of reassortment in all segments but the matrix protein gene (MP), which presents as multiple smaller clusters associated with di�erent European viruses. Ancestral reconstruction of host states of the hemagglutinin (HA) gene of viruses involved in the outbreaks suggests that transmission is driven by domestic ducks into galliform poultry. Thus, according to present evidence, we suggest the surveillance of domestic ducks as they are an epidemiologically relevant species for subclinical infection. Monitoring the spread due to movement between farms within regions and links to poultry production systems in European countries can help to predict and prevent future outbreaks.
The lineage which caused the largest recorded poultry epidemic in Europe continues to circulate, and the risk of further transmission by wild birds during migration remains.


Venkatesh, D., Brouwer, A., Goujgoulova, G., Ellis, R., Seekings, J., Brown, I., & Lewis, N. (2020). Regional Transmission and Reassortment of Highly Pathogenic Avian Influenza (HPAI) Viruses in Bulgarian Poultry 2017/18. Viruses, 12(6), 605

Journal Article Type Article
Acceptance Date May 28, 2020
Publication Date Jun 1, 2020
Deposit Date Jun 12, 2020
Publicly Available Date Jun 12, 2020
Journal Viruses
Publisher MDPI
Peer Reviewed Peer Reviewed
Volume 12
Issue 6
Pages 605
Public URL
Publisher URL


12719_Regional-Transmission-and-Reassortment-of- (9.1 Mb)

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