Numbers

Outbreaks of bird flu in Europe

Since 2014, the highly pathogenic form of the bird flu virus (highly pathogenic H5Nx-influenza strains) has occurred regularly in Europe. Since 2016, this has been the “clade 2.3.4.4b H5” strain.

Season

Number of outbreaks in Europe

2016-2017

2,781

2017-2018

166

2018-2019

21

2019-2020

334

2020-2021

3,559

 

2016-2017 2017-2018
2018-2019 2019-2020
2020-2021  
 

Figure 1: Representation of the outbreaks in the various clade 2.3.4.4b HPAI-H5 seasons since 2016 (source: EFSA). Circle = outbreak in poultry, star = outbreak in wild birds, triangle = outbreak in birds living in captivity.

The type of virus currently circulating is especially virulent for both poultry and birds living in the wild. The European Food Safety Authority (EFSA) has labeled the bird flu outbreak of the winter of 2020-2021 the most devastating and long-lasting epidemic of highly pathogenic avian influenza (HPAI) that has ever occurred in Europe.

Bird Flu in Belgium

Only two outbreaks of HPH5Nx were observed in 2020 whereas, in 2021, the Belgian NRL for Avian Influenza confirmed 11 outbreaks on farms (6) and in animals living in captivity, and all of this without any real interruption over the summer period. A remarkable development because, up to then, the outbreaks of the influenza virus occurred primarily in the winter period and there was a characteristic “summer break”. The loss of seasonality could indicate persistent circulation of the virus in animals living in the wild.

The autumn migration of wild birds in 2021 breathed new life into the epidemic, bringing with it a stream of new highly pathogenic H5Nx-viruses. The first positive wild bird of the new wave in Belgium was confirmed on 12 November 2021, and was followed by the first positive poultry business on 8 December 2021. The 2021-2022 bird-flu season was testament to the usefulness of the surveillance of wild birds as a warning system.

In 2021, 30 wild birds, such as geese, ducks, birds of prey and coastal birds, tested positive for the highly-pathogenic H5Nx-strain of the virus. Within one month (January 2022), there were an additional 30 new detections in wild birds, meaning there was a lot of (highly-pathogenic H5) bird-flu virus circulating among these animals (high infection levels) at the time. These cases in wild birds were primarily detected in the north of our country, which is particularly densely populated with water birds, but which is also where the vast majority of our poultry businesses are located. The first wild bird to test positive in Wallonia was reported on 9 February 2021 in the province of Liège.

Figure 2: Overview of the highly-pathogenic H5N1 detections in Belgium in wild birds (red) and in the sector (orange), combined with the poultry density in the different municipalities.

Despite the large number of wild birds that test positive for highly-pathogenic bird flu and the high infection levels in nature, the number of infections in the poultry sector remains limited (only 1 in January 2022) and there are no secondary infections in areas with a lot of poultry businesses (situation at the start of February 2022). That demonstrates the high vigilance that this sector has implemented to avoid introductions of the virus in their sheds. This also confirms the usefulness of the measures that apply in the event of increased vigilance and an outbreak in a business.

More info on the webpage of the NRL Avian Influenza.

Sciensano is the Belgian National Reference Laboratory (NRL) for avian influenza. To tackle this highly-contagious virus, which is able to cause fatal epidemics in birds, we participate in active and passive monitoring of our Belgian flocks and develop tools to diagnose the disease quickly and effectively and thus to prevent its expansion.

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