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Taft AS, Ozawa M, Fitch A, Depasse JV, Halfmann PJ, Hill-Batorski L, Hatta M, Friedrich TC, Lopes TJ, Maher EA, Ghedin E, Macken CA, Neumann G and Kawaoka Y, 2015. Identification of mammalian-adapting mutations in the polymerase complex of an avian H5N1 influenza virus. Nat Commun, 6:7491. doi: 10.1038/ncomms8491

UFHealth (University of Florida Helath), online. A first: Avian influenza detected in American dolphin. Available online: [https://ufhealth.org/news/2022/first-avian-influenza-detected-american-dolphin](https://ufhealth.org/news/2022/first-avian-influenza-detected-american-dolphin) [Accessed: 11 July 2023].

UH 50, online. Filadelfia: Aparece tercer foco de gripe aviar en el Chaco. Available online: [https://www.ultimahora.com/filadelfia-aparece-tercer-foco-gripe-aviar-el-chacon3063708](https://www.ultimahora.com/filadelfia-aparece-tercer-foco-gripe-aviar-el-chacon3063708) [Accessed: 11 July 2023].

USDA (U.S. Department of Agriculture), online. 2022 Detections of Highly Pathogenic Avian Influenza in Mammals. Available online: [https://www.aphis.usda.gov/aphis/ourfocus/animalhealth/animal-disease-information/avian/avian-influenza/hpai-2022/2022-hpai-mammals](https://www.aphis.usda.gov/aphis/ourfocus/animalhealth/animal-disease-information/avian/avian-influenza/hpai-2022/2022-hpai-mammals) [Accessed: 16 December 2022].

Volgelbescherming, online. Large tern chicks die en masse from bird flu. Available online: [https://www.vogelbescherming.nl/actueel/bericht/vogelbescherming-grote-zorgen-over-massale-sterfte-onder-grote-stern-kuikens-door-vogelgriep](https://www.vogelbescherming.nl/actueel/bericht/vogelbescherming-grote-zorgen-over-massale-sterfte-onder-grote-stern-kuikens-door-vogelgriep) [Accessed: 11 July 2023].

Volgelbescherming, online. Numbers of sandwich terns in 2023: half less than in previous years. Available online: [https://www.vogelbescherming.nl/actueel/bericht/aantallen-grote-sterns-in-2023-helft-minder-dan-vorig-jaren](https://www.vogelbescherming.nl/actueel/bericht/aantallen-grote-sterns-in-2023-helft-minder-dan-vorig-jaren) [Accessed: 11 July 2023].

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Taft AS, Ozawa M, Fitch A, Depasse JV, Halfmann PJ, Hill-Batorski L, Hatta M, Friedrich TC, Lopes TJ, Maher EA, Ghedin E, Macken CA, Neumann G and Kawaoka Y, 2015. Identification of mammalian-adapting mutations in the polymerase complex of an avian H5N1 influenza virus. Nat Commun, 6:7491. doi: 10.1038/ncomms8491

UFHealth (University of Florida Helath), online. A first: Avian influenza detected in American dolphin. Available online: [https://ufhealth.org/news/2022/first-avian-influenza-detected-american-dolphin](https://ufhealth.org/news/2022/first-avian-influenza-detected-american-dolphin) [Accessed: 11 July 2023].

UH 50, online. Filadelfia: Aparece tercer foco de gripe aviar en el Chaco. Available online: [https://www.ultimahora.com/filadelfia-aparece-tercer-foco-gripe-aviar-el-chaco-n3063708](https://www.ultimahora.com/filadelfia-aparece-tercer-foco-gripe-aviar-el-chaco-n3063708) [Accessed: 11 July 2023].

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Volgelbescherming, online. Large tern chicks die en masse from bird flu. Available online: [https://www.vogelbescherming.nl/actueel/bericht/vogelbescherming-grote-zorgen-over-massale-sterfte-onder-grote-stern-kuikens-door-vogelgriep](https://www.vogelbescherming.nl/actueel/bericht/vogelbescherming-grote-zorgen-over-massale-sterfte-onder-grote-stern-kuikens-door-vogelgriep) [Accessed: 11 July 2023].

Volgelbescherming, online. Numbers of sandwich terns in 2023: half less than in previous years. Available online: [https://www.vogelbescherming.nl/actueel/bericht/aantallen-grote-sterns-in-2023-helft-minder-dan-vorig-jaren](https://www.vogelbescherming.nl/actueel/bericht/aantallen-grote-sterns-in-2023-helft-minder-dan-vorig-jaren) [Accessed: 11 July 2023].

WHO (World Health Organization), 2020. Antigenic and genetic characteristics of zoonotic influenza A viruses and development of candidate vaccine viruses for pandemic preparedness. Geneva, WHO. 15 pp. Available online: [https://apps.who.int/iris/handle/10665/336259](https://apps.who.int/iris/handle/10665/336259)
WHO (World Health Organization), 2022. Assessment of risk associated with recent influenza A(H5N1) clade 2.3.4.4b viruses. Geneva. 3 pp. Available online: https://cdn.who.int/media/docs/default-source/influenza/avian-and-other-zoonotic-influenza/h5-risk-assessment-dec-2022.pdf?sfvrsn=a496333a_1&download=true

WHO (World Health Organization), 2023a. Avian Influenza Weekly Update Number 890: Human infection with avian influenza A(H5) viruses. Geneva. 4 pp. Available online: https://cdn.who.int/media/docs/default-source/wpro-- documents/emergency/surveillance/avian- influenza/ai_20230623.pdf?sfvrsn=5f006f99_116&Status=Master

WHO (World Health Organization), 2023b. Avian Influenza Weekly Update Number 901: Human infection with avian influenza A(H5) viruses. Geneva. 4 pp. Available online: https://apps.who.int/iris/bitstream/handle/10665/365675/AI- 20230407.pdf?sequence=227&isAllowed=y

WHO (World Health Organization), 2023c. Genetic and antigenic characteristics of zoonotic influenza A viruses and development of candidate vaccine viruses for pandemic preparedness. Geneva. 12 pp. Available online: https://cdn.who.int/media/docs/default-source/influenza/who-influenza- recommendations/vcm-northern-hemisphere-recommendation-2023- 2024/20230224_zoonotic_recommendations.pdf?sfvrsn=38c739fa_4

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WUR (Wageningen University Research), online. Bird flu (H5N1) detected in a fox with neurological symptoms. Available online: https://www.wur.nl/en/research- results/research-institutes/bioveterinary-research/show-bvr/bird-flu-h5n1- detected-in-a-fox-with-neurological-symptoms.htm [Accessed: 30 March 2022].

Xunta de Galicia, online. La Xunta detecta un foco de influenza aviar en una explotación de visones en la provincia de A Coruña. Available online: https://www.xunta.gal/notas-de-prensa/-/nova/73686/xunta-detecta-foco- influenza-aviar-una-explotacion-visones-provincia-coruna [Accessed: 16 December 2022].

Yamada S, Hatta M, Staker BL, Watanabe S, Imai M, Shinya K, Sakai-Tagawa Y, Ito M, Ozawa M, Watanabe T, Sakabe S, Li C, Kim JH, Myler PJ, Phan I, Raymond A, Smith E, Stacy R, Nidom CA, Lank SM, Wiseman RW, Bimber BN, O'Connor DH, Neumann G, Stewart LJ and Kawaoka Y, 2010. Biological and structural characterization of a host-adapting amino acid in influenza virus. PLoS Pathog, 6:e1001034. doi: 10.1371/journal.ppat.1001034

Zhu W Fau - Li X, Li X Fau - Dong J, Dong J Fau - Bo H, Bo H Fau - Liu J, Liu J Fau - Yang J, Yang J Fau - Zhang Y, Zhang Y Fau - Wei H, Wei H Fau - Huang W, Huang W Fau - Zhao X, Zhao X Fau - Chen T, Chen T Fau - Yang J, Yang J Fau - Li Z, Li Z Fau - Zeng X, Zeng X Fau - Li C, Li C Fau - Tang J, Tang J Fau - Xin L, Xin L Fau - Gao R, Gao R Fau - Liu L, Liu L Fau - Tan M, Tan M Fau - Shu Y, Shu Y Fau - Yang L, Yang
WHO (World Health Organization), 2022. Assessment of risk associated with recent influenza A(H5N1) clade 2.3.4.4b viruses. Geneva. 3 pp. Available online: https://cdn.who.int/media/docs/default-source/influenza/avian-and-other-zoonotic-influenza/h5-risk-assessment-dec-2022.pdf?sfvrsn=a496333a_1&download=true

WHO (World Health Organization), 2023a. Avian Influenza Weekly Update Number 890: Human infection with avian influenza A(H5) viruses. Geneva. 4 pp. Available online: https://cdn.who.int/media/docs/default-source/wpro-- documents/emergency/surveillance/avian- influenza/ai_20230623.pdf?sfvrsn=5f006f99_116&Status=Master

WHO (World Health Organization), 2023b. Avian Influenza Weekly Update Number 901: Human infection with avian influenza A(H5) viruses. Geneva. 4 pp. Available online: https://apps.who.int/iris/bitstream/handle/10665/365675/AI- 20230407.pdf?sequence=227&isAllowed=y

WHO (World Health Organization), 2023c. Genetic and antigenic characteristics of zoonotic influenza A viruses and development of candidate vaccine viruses for pandemic preparedness. Geneva. 12 pp. Available online: https://cdn.who.int/media/docs/default-source/influenza/who-influenza- recommendations/vcm-northern-hemisphere-recommendation-2023- 2024/20230224_zoonotic_recommendations.pdf?sfvrsn=38c739fa_4

WHO (World Health Organization), online. Avian Influenza A (H5N1) - Spain. Available online: https://www.who.int/emergencies/disease-outbreak-news/item/2022- DON420 [Accessed: 16 December 2022].

WOAH (World Organisation for Animal Health), online. Guinea - Influenza A viruses of high pathogenicity (Inf. with) (non-poultry including wild birds) (2017-) - Immediate notification. Available online: https://wahis.woah.org/#/in-review/5048 [Accessed: 11 July 2023].

WOAH (World Organisation for Animal Health), online. Immediate notification/ Highly pathogenic influenza A viruses (Inf. with)(non-poultry including wild birds)(2017-), Estonia. Available online: https://wahis.oie.int/#/report-info?reportId=44804 [Accessed: 21 December 2021].

WOAH (World Organisation for Animal Health), online. World Animal Health Information Database (WAHIS) Interface. Available online: https://wahis.woah.org/#/home [Accessed: 8 March 2023].

WOAH, online. World Animal Health Information Database (WAHIS) Interface. Available online: https://wahis.woah.org/#/in-event/5037/dashboard [Accessed: 11 July 2023].

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# Appendix A – Terms of Reference

## A.1. Background and Terms of Reference as provided by the requestor

Avian influenza is an infectious viral disease in birds, including domestic poultry. Infections with avian influenza viruses in poultry cause two main forms of that disease that are distinguished by their virulence. The low pathogenic (LPAI) form generally only causes mild symptoms, while the highly pathogenic (HPAI) form results in very high mortality rates in most poultry species. That disease may have a severe impact on the profitability of poultry farming.

Avian influenza is mainly found in birds, but under certain circumstances infections can also occur in humans even though the risk is generally very low.

More than a decade ago, it was discovered that virus acquired the capability to be carried by wild birds over long distances. This occurred for the HPAI of the subtype A(H5N1) from South East and Far East Asia to other parts of Asia, Europe and Africa as well as to North America. In the current epidemic the extent of the wild bird involvement in the epidemiology of the disease is exceptional.

Since late October 2016 up to early February 2017, highly pathogenic avian influenza (HPAI) of the subtype A(H5N8) has been detected in wild migratory birds or captive birds on the territory of 21 Member States, namely Austria, Belgium, Bulgaria, Croatia, Czechia, Denmark, Finland, France, Germany, Greece, Hungary, Ireland, Italy, the Netherlands, Poland, Portugal, Slovakia, Slovenia, Spain, Sweden and the United Kingdom. In 17 Member States the virus has spilled over to poultry holdings leading also to lateral spread between holdings in a few Member States, in particular in those with a high density of duck and geese holdings where the poultry cannot sufficiently be protected against contacts with wild birds. A second HPAI subtype A(H5N5) has been detected in wild birds and recently also in poultry holdings in Germany.

The number of infected migratory wild birds found dead and the geographic extent of these findings are posing an immense threat for virus introduction into poultry or captive birds holdings as demonstrated by the high number of outbreaks (~700 as of 08/02/2017).

In the event of an outbreak of avian influenza, there is a risk that the disease agent might spread to other holdings where poultry or other captive birds are kept. As a result, it may spread from one Member State to other Member States or to third countries through trade in live birds or their products.

There is knowledge, legislation, technical and financial tools in the EU to effectively deal with outbreaks of avian influenza in poultry and captive birds. However, the very wide virus spread by wild birds and the increased risk of direct or indirect virus introduction into poultry or captive bird holdings has led to the largest HPAI epidemic in the EU so far. This situation calls for a reflection and evaluation how preparedness, risk assessment, early detection and control measures could be improved.

The Commission and Member States are therefore in need of an epidemiological analysis based on the data collected from the disease affected Member States. The use of the EFSA Data Collection Framework is encouraged given it promotes the harmonisation
# Appendix A – Terms of Reference

## A.1. Background and Terms of Reference as provided by the requestor

Avian influenza is an infectious viral disease in birds, including domestic poultry. Infections with avian influenza viruses in poultry cause two main forms of that disease that are distinguished by their virulence. The low pathogenic (LPAI) form generally only causes mild symptoms, while the highly pathogenic (HPAI) form results in very high mortality rates in most poultry species. That disease may have a severe impact on the profitability of poultry farming.

Avian influenza is mainly found in birds, but under certain circumstances infections can also occur in humans even though the risk is generally very low.

More than a decade ago, it was discovered that virus acquired the capability to be carried by wild birds over long distances. This occurred for the HPAI of the subtype A(H5N1) from South East and Far East Asia to other parts of Asia, Europe and Africa as well as to North America. In the current epidemic the extent of the wild bird involvement in the epidemiology of the disease is exceptional.

Since late October 2016 up to early February 2017, highly pathogenic avian influenza (HPAI) of the subtype A(H5N8) has been detected in wild migratory birds or captive birds on the territory of 21 Member States, namely Austria, Belgium, Bulgaria, Croatia, Czechia, Denmark, Finland, France, Germany, Greece, Hungary, Ireland, Italy, the Netherlands, Poland, Portugal, Slovakia, Slovenia, Spain, Sweden and the United Kingdom. In 17 Member States the virus has spilled over to poultry holdings leading also to lateral spread between holdings in a few Member States, in particular in those with a high density of duck and geese holdings where the poultry cannot sufficiently be protected against contacts with wild birds. A second HPAI subtype A(H5N5) has been detected in wild birds and recently also in poultry holdings in Germany.

The number of infected migratory wild birds found dead and the geographic extent of these findings are posing an immense threat for virus introduction into poultry or captive birds holdings as demonstrated by the high number of outbreaks (~700 as of 08/02/2017).

In the event of an outbreak of avian influenza, there is a risk that the disease agent might spread to other holdings where poultry or other captive birds are kept. As a result, it may spread from one Member State to other Member States or to third countries through trade in live birds or their products.

There is knowledge, legislation, technical and financial tools in the EU to effectively deal with outbreaks of avian influenza in poultry and captive birds. However, the very wide virus spread by wild birds and the increased risk of direct or indirect virus introduction into poultry or captive bird holdings has led to the largest HPAI epidemic in the EU so far. This situation calls for a reflection and evaluation how preparedness, risk assessment, early detection and control measures could be improved.

The Commission and Member States are therefore in need of an epidemiological analysis based on the data collected from the disease affected Member States. The use of the EFSA Data Collection Framework is encouraged given it promotes the harmonisation
of data collection. Any data that is available from neighbouring third countries should be
used as well, if relevant.

Therefore, in the context of Article 31 of Regulation (EC) No. 178/2002¹³, EFSA should
provide the technical and scientific assistance to the Commission based on the following
Terms of Reference (TOR):

1) Analyse the epidemiological data on highly pathogenic avian influenza (HPAI) and low pathogenic avian influenza (LPAI), where co-circulating or linked within the same epidemic, from HPAI disease affected Member States.

2) Analyse the temporal and spatial pattern of HPAI and LPAI as appropriate in poultry, captive birds and wild birds, as well the risk factors involved in the occurrence, spread and persistence of the HPAI virus in and at the interface of these avian populations.

3) Based on the findings from the points above, describe the effect of prevention and control measures.

4) Provide for regular quarterly reports updating on the avian influenza situation within the Union and worldwide, in particular with a view to describe the evolution of virus spread from certain regions towards the EU. In case of significant changes in the epidemiology of avian influenza, these reports could be needed more frequently. These reports should in particular closely follow the developments of zoonotic avian influenza viruses (such as HPAI A(H5N6) and LPAI A(H7N9)) in collaboration with the European Centre for Disease Prevention and Control (ECDC).

A.2 Interpretation of the Terms of Reference

In reply to ToR 1 and ToR 2, this scientific report gives an overview of the HPAI and LPAI outbreaks in poultry, captive and wild birds detected in Europe from 29 April to 23 June 2023 and reported by Member States and neighbouring countries to the ADIS or WOAH. Member States where avian influenza outbreaks have occurred in poultry have submitted additional epidemiological data to EFSA, that have been used to analyse the characteristics of the affected poultry establishments.

It was not possible to collect data for a risk factor analysis on the occurrence and persistence of HPAI virus within the EU. Risk factor analysis requires not only case-related information, but also data on the susceptible population (e.g. location of establishments, population structure), which should be collected in a harmonised manner across the EU. Limitations in data collection, reporting and analysis were explained in the first avian influenza overview report (EFSA et al., 2017).

If HPAI outbreaks in poultry are detected in the EU, a description of the applied prevention and control measures (ToR 3) is given in the overview document provided by representatives from the affected Member States and is provided in Annex A. Information was collected for outbreaks that occurred from 3 April to 9 June 2023. The main topics covered are increasing awareness, release and repeal of housing orders, strengthening

<footnote n="13">¹³ Regulation (EC) No 178/2002 of the European Parliament and of the Council of 28 January 2002 laying down the general principles and requirements of food law, establishing the European Food Safety Authority and laying down procedures in matters of food safety. OJ L 31, 1.2.2002, pp. 1–24.</footnote>
of data collection. Any data that is available from neighbouring third countries should be
used as well, if relevant.

Therefore, in the context of Article 31 of Regulation (EC) No. 178/2002¹³, EFSA should
provide the technical and scientific assistance to the Commission based on the following
Terms of Reference (TOR):

1) Analyse the epidemiological data on highly pathogenic avian influenza (HPAI) and low pathogenic avian influenza (LPAI), where co-circulating or linked within the same epidemic, from HPAI disease affected Member States.

2) Analyse the temporal and spatial pattern of HPAI and LPAI as appropriate in poultry, captive birds and wild birds, as well the risk factors involved in the occurrence, spread and persistence of the HPAI virus in and at the interface of these avian populations.

3) Based on the findings from the points above, describe the effect of prevention and control measures.

4) Provide for regular quarterly reports updating on the avian influenza situation within the Union and worldwide, in particular with a view to describe the evolution of virus spread from certain regions towards the EU. In case of significant changes in the epidemiology of avian influenza, these reports could be needed more frequently. These reports should in particular closely follow the developments of zoonotic avian influenza viruses (such as HPAI A(H5N6) and LPAI A(H7N9)) in collaboration with the European Centre for Disease Prevention and Control (ECDC).

A.2 Interpretation of the Terms of Reference

In reply to ToR 1 and ToR 2, this scientific report gives an overview of the HPAI and LPAI outbreaks in poultry, captive and wild birds detected in Europe from 29 April to 23 June 2023 and reported by Member States and neighbouring countries to the ADIS or WOAH. Member States where avian influenza outbreaks have occurred in poultry have submitted additional epidemiological data to EFSA, that have been used to analyse the characteristics of the affected poultry establishments.

It was not possible to collect data for a risk factor analysis on the occurrence and persistence of HPAI virus within the EU. Risk factor analysis requires not only case-related information, but also data on the susceptible population (e.g. location of establishments, population structure), which should be collected in a harmonised manner across the EU. Limitations in data collection, reporting and analysis were explained in the first avian influenza overview report (EFSA et al., 2017).

If HPAI outbreaks in poultry are detected in the EU, a description of the applied prevention and control measures (ToR 3) is given in the overview document provided by representatives from the affected Member States and is provided in Annex A. Information was collected for outbreaks that occurred from 3 April to 9 June 2023. The main topics covered are increasing awareness, release and repeal of housing orders, strengthening

<footnote n="13">¹³ Regulation (EC) No 178/2002 of the European Parliament and of the Council of 28 January 2002 laying down the general principles and requirements of food law, establishing the European Food Safety Authority and laying down procedures in matters of food safety. OJ L 31, 1.2.2002, pp. 1–24.</footnote>
biosecurity, preventive culling, implementation of a regional standstill, bans on hunting and derogations from restriction zone implementation after a risk assessment.

Monitoring of the avian influenza situation in other countries (ToR 4) is based on data reported to WOAH. The description focuses only on findings of avian influenza viruses occurring in countries that are considered to be of epidemiological interest for the EU/EEA and the UK or of public health relevance, specifically on HPAI A(H5N1), HPAI A(H5N2), HPAI A(H5N5), HPAI A(H5N6), HPAI A(H5N8), HPAI/LPAI A(H7N9) and LPAI A(H9N2). The background and epidemiology, detections, phenotypic and genetic characterisations are described based on information from confirmed human, poultry and wild bird cases that occurred from 29 April to 23 June 2023. Possible actions for preparedness in the EU are discussed.

This report mainly describes information that has become available since the publication of the EFSA report for the period March to April 2023 (EFSA et al. 2023b) and that might affect the interpretation of risks related to avian influenza introduction and/or spread in Europe.
biosecurity, preventive culling, implementation of a regional standstill, bans on hunting and derogations from restriction zone implementation after a risk assessment.

Monitoring of the avian influenza situation in other countries (ToR 4) is based on data reported to WOAH. The description focuses only on findings of avian influenza viruses occurring in countries that are considered to be of epidemiological interest for the EU/EEA and the UK or of public health relevance, specifically on HPAI A(H5N1), HPAI A(H5N2), HPAI A(H5N5), HPAI A(H5N6), HPAI A(H5N8), HPAI/LPAI A(H7N9) and LPAI A(H9N2). The background and epidemiology, detections, phenotypic and genetic characterisations are described based on information from confirmed human, poultry and wild bird cases that occurred from 29 April to 23 June 2023. Possible actions for preparedness in the EU are discussed.

This report mainly describes information that has become available since the publication of the EFSA report for the period March to April 2023 (EFSA et al. 2023b) and that might affect the interpretation of risks related to avian influenza introduction and/or spread in Europe.
# Appendix B – Data and Methodologies

## B.1 Data on animals

### B.1.1 Overview of avian influenza outbreaks in Europe (ToR 1 and ToR 2)

Data on the avian influenza outbreaks that occurred in Europe from 29 April to 23 June 2023 submitted by Member States to the ADIS (European Commission, online) were taken into account for this report. Data extraction was carried on 23 June 2023. WOAH-WAHIS ((WOAH, online-d) was consulted to complement the information for European countries not reporting HPAI notifications to ADIS. In addition, HPAI-affected European countries were asked to provide more detailed epidemiological data directly to EFSA on the avian influenza outbreaks that occurred in poultry up to 9 June 2023. Wild bird species have been categorised according to Table A.3 in Annex A, and the common and scientific names of wild bird species described in this report in relation to Europe are reported in Table A.4 in Annex A. The public GISAID's EpiFlu™ Database was accessed to download newly released avian influenza virus sequences.

The annexes to this Scientific Report are available on the EFSA Knowledge Junction community on Zenodo at: https://doi.org/10.5281/zenodo.8133701

### B.1.2 Overview of avian influenza outbreaks in other countries not reporting via ADIS (ToR 4)

Data from WOAH-WAHIS (WOAH, online-d) on HPAI A(H5N1), A(H5N2), A(H5N5), A(H5N6), A(H5N8) and LPAI A(H7N9) in domestic and wild birds were used to describe and map the geographic distribution of avian influenza virus detections in domestic and wild birds in Africa, the Americas, Asia and Europe based on the observation dates. Data were retrieved on 29 June 2023 and extracted by EFSA. They were used and reproduced with permission. WOAH bears no responsibility for the integrity or accuracy of the data contained herein, but not limited to, any deletion, manipulation, or reformatting of data that may have occurred beyond its control.

### B.1.2 Genetic characterisation of avian influenza viruses: description of the nomenclature of the HPAI A(H5) viruses used in the document

The HA gene of clade 2.3.4.4 A(H5) viruses has rapidly evolved since the most recent official update of the nomenclature of the A/goose/Guangdong/1/1996-lineage H5Nx virus (Smith et al., 2015). This clade emerged in China in 2008 and since then it has acquired various neuraminidase subtypes, including N1, N2, N3, N4, N5, N6 and N8, by reassortments with other avian influenza viruses from different regions, and has evolved into several subgroups. While a revised nomenclature of clade 2.3.4.4 viruses is pending, in previous reports we used the genetic clustering described in 2018 by Lee and co-authors, who recognised four groups (a-d) within clade 2.3.4.4 (Lee et al., 2018). Recently, an update to the unified nomenclature for clade 2.3.4.4 A(H5) viruses has been proposed by the WHO (WHO, 2020) and eight genetic groups (a-h) have been recognised. To align the nomenclature system between international organisations this classification has been adopted for this report. Based on this proposed clustering, A(H5) viruses of clades 2.3.4.4a and d-h have mainly been circulating in poultry in Asia, while clades 2.3.4.4b and 2.3.4.4c have spread globally through wild bird migrations during 2014–2015 (2.3.4.4c) and from 2016 to the present day (2.3.4.4b). A list with the distribution of the different genetic
# Appendix B – Data and Methodologies

## B.1 Data on animals

### B.1.1 Overview of avian influenza outbreaks in Europe (ToR 1 and ToR 2)

Data on the avian influenza outbreaks that occurred in Europe from 29 April to 23 June 2023 submitted by Member States to the ADIS (European Commission, online) were taken into account for this report. Data extraction was carried on 23 June 2023. WOAH-WAHIS ((WOAH, online-d) was consulted to complement the information for European countries not reporting HPAI notifications to ADIS. In addition, HPAI-affected European countries were asked to provide more detailed epidemiological data directly to EFSA on the avian influenza outbreaks that occurred in poultry up to 9 June 2023. Wild bird species have been categorised according to Table A.3 in Annex A, and the common and scientific names of wild bird species described in this report in relation to Europe are reported in Table A.4 in Annex A. The public GISAID's EpiFlu™ Database was accessed to download newly released avian influenza virus sequences.

The annexes to this Scientific Report are available on the EFSA Knowledge Junction community on Zenodo at: https://doi.org/10.5281/zenodo.8133701

### B.1.2 Overview of avian influenza outbreaks in other countries not reporting via ADIS (ToR 4)

Data from WOAH-WAHIS (WOAH, online-d) on HPAI A(H5N1), A(H5N2), A(H5N5), A(H5N6), A(H5N8) and LPAI A(H7N9) in domestic and wild birds were used to describe and map the geographic distribution of avian influenza virus detections in domestic and wild birds in Africa, the Americas, Asia and Europe based on the observation dates. Data were retrieved on 29 June 2023 and extracted by EFSA. They were used and reproduced with permission. WOAH bears no responsibility for the integrity or accuracy of the data contained herein, but not limited to, any deletion, manipulation, or reformatting of data that may have occurred beyond its control.

### B.1.2 Genetic characterisation of avian influenza viruses: description of the nomenclature of the HPAI A(H5) viruses used in the document

The HA gene of clade 2.3.4.4 A(H5) viruses has rapidly evolved since the most recent official update of the nomenclature of the A/goose/Guangdong/1/1996-lineage H5Nx virus (Smith et al., 2015). This clade emerged in China in 2008 and since then it has acquired various neuraminidase subtypes, including N1, N2, N3, N4, N5, N6 and N8, by reassortments with other avian influenza viruses from different regions, and has evolved into several subgroups. While a revised nomenclature of clade 2.3.4.4 viruses is pending, in previous reports we used the genetic clustering described in 2018 by Lee and co-authors, who recognised four groups (a-d) within clade 2.3.4.4 (Lee et al., 2018). Recently, an update to the unified nomenclature for clade 2.3.4.4 A(H5) viruses has been proposed by the WHO (WHO, 2020) and eight genetic groups (a-h) have been recognised. To align the nomenclature system between international organisations this classification has been adopted for this report. Based on this proposed clustering, A(H5) viruses of clades 2.3.4.4a and d-h have mainly been circulating in poultry in Asia, while clades 2.3.4.4b and 2.3.4.4c have spread globally through wild bird migrations during 2014–2015 (2.3.4.4c) and from 2016 to the present day (2.3.4.4b). A list with the distribution of the different genetic
clades reported by countries globally from birds, humans and the environment has been
published by WHO in February 2023 (WHO, 2023c).

B.2 Data on humans

The numbers of human cases caused by infection with avian influenza viruses were collected by ECDC. Multiple sources are scanned regularly as part of Epidemic Intelligence activities at ECDC to collect information on laboratory-confirmed human cases. Data were extracted and line lists developed to collect case-based information on virus type, date of disease onset, country of reporting, country of exposure, sex, age, exposure, clinical information (hospitalisation, severity) and outcome. All cases included in the line list and mentioned in the document have been laboratory-confirmed. Data are continuously checked for double entries and validity. The data on human cases cover the full period of time since the first human case was reported. Therefore, data on human cases refer to different time periods and are included irrespective of whether there have been any new human cases during the reporting period.
clades reported by countries globally from birds, humans and the environment has been published by WHO in February 2023 (WHO, 2023c).

## B.2 Data on humans

The numbers of human cases caused by infection with avian influenza viruses were collected by ECDC. Multiple sources are scanned regularly as part of Epidemic Intelligence activities at ECDC to collect information on laboratory-confirmed human cases. Data were extracted and line lists developed to collect case-based information on virus type, date of disease onset, country of reporting, country of exposure, sex, age, exposure, clinical information (hospitalisation, severity) and outcome. All cases included in the line list and mentioned in the document have been laboratory-confirmed. Data are continuously checked for double entries and validity. The data on human cases cover the full period of time since the first human case was reported. Therefore, data on human cases refer to different time periods and are included irrespective of whether there have been any new human cases during the reporting period.