Avian influenza overview December 2020 – February 2021

Abstract

Between 8 December 2020 and 23 February 2021, 1,022 highly pathogenic avian influenza (HPAI) virus detections were reported in 25 EU/EEA countries and the UK in poultry (n=592), wild (n=421) and captive birds (n=9).The majority of the detections were reported by France that accounted for 442 outbreaks in poultry, mostly located in the Landes region and affecting the foie gras production industry, and six wild bird detections; Germany, who reported 207 detections in wild birds and 50 poultry outbreaks; Denmark, with 63 detections in wild birds and one poultry outbreak; and Poland, with 37 poultry outbreaks and 24 wild bird detections. Due to the continued presence of HPAI A(H5) viruses in wild birds and the environment, there is still a risk of avian influenza incursions with the potential further spread between establishments, primarily in areas with high poultry densities. As the currently circulating HPAI A(H5N8) virus can cause high mortality also in affected duck farms, mortality events can be seen as a good indicator of virus presence. However, also subclinical virus spread in this type of poultry production system have been reported. To improve early detection of infection in poultry within the surveillance zone, the clinical inspection of duck establishments should be complemented by encouraging farmers to collect dead birds to be pooled and tested weekly (bucket sampling). Six different genotypes were identified to date in Europe and Russia, suggesting a high propensity of these viruses to undergo multiple reassortment events. To date, no evidence of fixation of known mutations previously described as associated to zoonotic potential has been observed in HPAI viruses currently circulanting in Europe based on the available sequences. Seven cases due to A(H5N8) HPAI virus have been reported from Russia, all were poultry workers with mild or no symptoms. Five human cases due to A(H5N6) HPAI and 10 cases due to A(H9N2) LPAI viruses have been reported from China. The risk for the general population as well as travel-related imported human cases is assessed as very low and the risk for people occupationally exposed people as low. Any human infections with avian influenza viruses are notifiable within 24 hours through the Early Warning and Response System (EWRS) and the International Health Regulations (IHR) notification system.

Isolation of clade 2.3.4.4b A(H5N8), a highly pathogenic avian influenza virus, from a worker during an outbreak on a poultry farm, Russia, December 2020

“…These epizooties have resulted in several economically costly poultry outbreaks and continue to pose a risk to agriculture and humans. Influenza viruses of the H5N6 subtype of clade 2.3.4.4 have been known to infect humans since 2014, and several cases have resulted in fatal outcomes [ 10 , 11 ]. Because of the potential risk of a pandemic, constant surveillance of the clade 2.3.4.4 A(H5) is considered essential [ 12 ].…”

Evolutionary Dynamics of H5 Highly Pathogenic Avian Influenza Viruses (Clade 2.3.4.4B) Circulating in Bulgaria in 2019–2021

“…In February 2021 a new introduction of HPAI H5N8 viruses of clade 2.3.4.4B was recorded in the northern region of Pleven. The 2021 HPAI H5N8 viruses (outbreaks 21/1-21/3, Table 1) cluster separately from the viruses previously detected in the country and show the highest identity with the HPAI H5N8 viruses, which have been circulating in Europe since October 2020 [12]; in particular the three Bulgarian viruses are almost identical and cluster with HPAI H5N8 viruses identified in Poland, England and Russia (Krasnodar Region) in November 2020 and January 2021 (Figures 1 and 2).…”

“…In October 2020, with the beginning of the migration of wild birds to their wintering areas, a new HPAI H5 incursion occurred in northern Europe. Similar to the 2016 epidemic wave, the virus had first been detected further east and arrived across a wide area causing variable mortality in the affected wild bird populations and rapidly spread to most of the European countries [9][10][11][12].…”

Phylodynamic assessment of control measures for highly pathogenic avian influenza epidemics in France

“…It resulted in 484 infected poultry farms and approximately 7 million culled birds [1]. It remains critically important to learn as much as possible from this devastating epidemic, particularly as France once again experienced an HPAI outbreak in December 2020 [2]. The 2016-17 epidemic was caused by an H5N8 virus of the lineage 2.3.4.4b (A/Gs/Gd/1/96 clade) of Asian origin that was likely introduced by migratory birds [3].…”