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Avian influenza (AI)


Fowl plague, Avian Flu, Highly Pathogenic Avian Influenza


  • Family: Orthomyxoviridae, genus: Influenzavirus A
  • Notifiable disease : Yes


Avian Influenza (AI)Influenza viruses are segmented negative strand RNA viruses that are placed in the family Orthomyxoviridae in three genera: Influenzavirus A, B and C. Only influenza A viruses have been reported to cause natural infections of birds.


Type A influenza viruses are further divided into subtypes based on the antigenic relationships in the surface glycoproteins haemagglutinin (H) and neuraminidase (N). At present 16 H (H1-H16) and 9 N subtypes (N1-N9) have been recognised. Each virus has one H and one N antigen, apparently in any combination; all subtypes and the majority of possible combinations have been isolated from wild avian species.


Current EU legislation (CEC, 1992) defines avian influenza as "an infection of poultry caused by any influenza A virus which has an IVPI in six-week-old chickens greater than 1.2 or any infection with influenza A viruses of H5 or H7 subtype for which nucleotide sequencing has demonstrated the presence of multiple basic amino acids at the cleavage site of the hemagglutinin".


However it has been proved that H5 and H7 HPAI emerge in poultry from LPAI progenitors. Considering that the economic impact of crisis could be reduced by anticipated control measures, the new EU definition proposed for avian influenza is thus defined now as "an infection of poultry or other birds caused by any influenza A virus of the H5 or H7 subtype or by any influenza virus with an IVPI greater than 1.2".

This means that the term avian influenza applies now to all viruses of the H5 or H7 subtype regardless of the virulence for poultry.
Avian influenza represents a considerable threat to the poultry industry, with huge economic impact.Avian Influenza (AI)


H5N1 in Asia is an unprecedented event in the story of influenza considering its huge distribution and endemicity, its highest virulence and expanding host range. The lack of early warning systems and rapid control in Asian countries has allowed the circulation and evolution of the virus leading to increased virulence (Z genotype) and adaptation to new hosts like ducks, wild birds and mammals.
In this context, each movement can become a high risk factor (trade, traffic, migration...).


An H7N9 virus emerged for the first time in a man in Shanghai in March 2003, and has already been responsible for 43 deaths (according to the WHO as at 15 July 2013) for 134 infected cases recorded. The virulence of this subtype is high in humans. It kills in fifteen days in one case out of five and its morbidity rate exceeds that of the H5N1. Fortunately, as in the case of the H5N1 virus, no inter-human transmission - an essential condition for an influenza virus to become a pandemic - has been reported to date. Nevertheless, unlike the H5N1 virus, this is only a low pathogenic avian influenza (LPAI) virus, calling to question of role of birds as a reservoir and making the surveillance thereof necessarily difficult when corpses of birds fallen victim to the H5N1 were an indicator.


Avian influenza viruses are very variable and largely unpredictable regarding the risk posed for animal and human health. They cannot be eradicated from wild bird reservoirs and, once introduced in domestic poultry, their control is often difficult. For all these reasons, they represent a considerable challenge for scientists, decision makers and risk managers and emphasize the need for collaboration between public and animal health authorities.


Numerous studies on the evolution of avian influenza viruses and acquisition of virulence during circulation in chickens have clearly demonstrated that each H5 and H7 viruses is potentially dangerous. The chance of mutation of a LPAI into a HPAI is uncertain and will depend on many factors.

Given the zoonotic potential of certain avian influenzas, it is necessary to monitor the situation on the ground and to prepare for a crisis.



CODA-CERVA is the Belgian National Reference Laboratory for Avian Influenza.
Avian Influenza (AI)Tests performed
- Virus isolation, Ag-ELISA, real-time RT-PCR
- Sequencing and biocomputing
- Serology: IHA, ELISA, SN tes


- Development of diagnostic tools and testing of vaccines
- Measurement of immunity (innate and acquired: humoral, cell-mediated, local)
- Pathogenesis (adaptation, virulence)
- Surveillance in wild birds


The laboratory has the necessary expertise and facilities to isolate the virus under safe conditions. The personnel are experienced in serological tests, virus isolation and molecular diagnosis of AI virus from clinical samples.


Th. van den Berg and S. Van Borm are members of the EFSA (European Food Safety Authority) AI expert panel. Th. Van den Berg and S. Marché are members of the OFFLU group (joint OIE (World Organisation for Animal Health) -FAO network of expertise on influenza). The laboratory organizes FAO (Food and Agriculture Organization of the United Nations) trainings on Avian Influenza.


Bénédicte Lambrecht
Sylvie Marché
Mieke Steensels
Fabienne Rauw


- De Vriese J., Steensels M., Palya V., Gerdin Y, Moore D.K., Lambrecht B., Van Borm St, van den Berg T. Passive protection afforded by maternally derived antibody in chickens and the antibody's interference with the protection elicited by AI inactivated vaccines in progeny. Avian dis, 2010, 54 suppl 1, 246-252.

- Domanska-Blichrarz K, Minta Z, Smietanka K., Marché S., van den Berg T. H5N1 high pathogenicity avian influenza virus survival in different types of water. Avian diseases, 2010,54 suppl 1, 734-37.

- Garigliany MM, Habyarimana A, Lambrecht B, Van de Paar E, Cornet A, van den Berg T, Desmecht D. Influenza A strain-dependent pathogenesis in fatal H1N1 and H5N1 subtype infections of mice. Emerg Infect Dis. 2010,16(4):595-603.

- Lage Ferreira H., Lambrecht B., Van Borm S, Torrieri-Dramard L., Klatzmann D., Bellier B, van den Berg T Dominant epitope in the Hemagglutinin of avian highly pathogenic avian influenza H5N1 clade 1 virus by selection of escape mutants. Avian diseases, 2010, 54 suppl 1, 565-71.

- Lage Ferreira H, Pirlot J-F, Kaspers B, Kothlow S., van den Berg T, Lambrecht B. Development of specific enzyme-linked-immunosorbent assay to evaluate the duck immune response after experimental infection with H5N1 and H7N1 low pathogenic avian influenza viruses. Avian diseases, 2010, 54 suppl 1, 660-67.

- Torrieri-Dramard L, Lambrecht B, Ferreira HL, van den Berg T, Klatzmann D, Bellier B. Intranasal DNA Vaccination Induces Potent Mucosal and Systemic Immune Responses and Cross-protective Immunity Against Influenza Viruses. Molecular Therapy. (19 October 2010) | doi:10.1038/mt.2010.222).

- Van Borm St., Lage Ferreira H., van den Berg T., Fine quantification of Avian Influenza H5N1 escape mutant quasispecies populations using mutation-specific real-time PCR. Avian diseases, 2010, 54 suppl 1,558-64.

- Van Borm St, Suarez D.L., Boschmans M, Ozhelvaci O., Marche S., van den Berg T. Rapid detection of Eurasian and American H7 subtype Influenza A. viruses using a single TaqManMGB real-time RT-PCR. Avian diseases, 2010, 54 suppl 1, 632-38.

- Marché S., van den Berg T. Evaluation of different strategies for the use of ELISA tests as first screening tools for serologic surveillance of low pathogenic avian influenza in the Belgian poultry sector. Avian diseases, 2010, 54 sup 1, 627-31

- Marché S., Lambrecht B ,van den Berg T. Evaluation of different serologic markers for the early detection of Avian Influenza infection of chickens. Avian diseases, 2010, 54 suppl 1, 690-698.

- Marché S., van den Berg T. Evaluation of rapid antigen detection kits for the diagnosis of highly pathogenic Avian Influenza H5N1 infection. Avian diseases, 2010,54 suppl 1, 650-654.

- Welby S., van den Berg T, Marché S., Houdart Ph, Hooyberghs, Mintiens K. Redesigning the serological surveillance program for notifiable avian influenza in Belgian professional poultry holdings. Avian diseases, 2010,54, 597-605.

- Brochier B, Vangeluwe D. & van den Berg T. Alien Invasive Birds. Rev. Sci. Tech. OIE. 2010, 29 (2), 217-225.

- Daviet S, Van Borm S, Habyarimana A, Ahanda ML, Morin V, Oudin A, van den Berg T, Zoorob R. Induction of Mx and PKR failed to protect chickens from H5N1 infection. Viral Immunol. 2009 Dec;22(6):467-72

- De Vleeschauwer A, Atanasova K, Van Borm S, van den Berg T, Rasmussen TB, Uttenthal A, Van Reeth K. Comparative pathogenesis of an avian H5N2 and a swine H1N1 influenza virus in pigs. PLoS One. 2009,4(8):e6662

- Koch G, Steensels M, van den Berg T. Vaccination of birds other than chickens and turkeys against avian influenza. Rev Sci Tech. 2009, 28(1):307-18

- Steensels M., Bublot M., Van Borm S, De Vriese J., Lambrecht B., Richard-Mazet A., Chanavat-Bizzini S., Duboeuf M., Le Gros FX, van den Berg T. Prime-boost vaccination with a fowlpox vector and an inactivated avian influenza vaccine is highly immunogenic in Pekin ducks challenged with Asian H5N1 HPAI. Vaccine. 2009 Jan 29;27(5):646-54.

- Van Reeth K, Braeckmans D, Cox E, Van Borm S, van den Berg T, Goddeeris B, De Vleeschauwer A. Prior infection with an H1N1 swine influenza virus partially protects pigs against a low pathogenic H5N1 avian influenza virus. Vaccine. 2009 Oct 23;27(45):6330-9.

- van den Berg T. The role of the legal and illegal trade of live birds and avian products in the spread of avian influenza. Rev sci tech Off Int Epiz, 2009,28(1),93-111


- Van den Berg, T. & Houdart P. (2008). Avian Influenza outbreak management: action at time of confirmation, depopulation and disposal methods; the "Belgian experience" during the H7N7 highly pathogenic avian influenza epidemic in 2003. Zoonoses and Public Health. 55, 1: 54-64.

- van den Berg, T, Lambrecht, B., Marché, S., Steensels, M., Van Borm, S. & Bublot M. (2008) . Influenza vaccines and vaccination strategies in birds. Comparative Immunology, Microbiology and Infectious Diseases. 31, 2-3: 121-165.


- Rauw, F, Lambrecht B. & van den Berg T. (2007). Pivotal role of ChIFNgamma in the pathogenesis and immunosuppression of Infectious Bursal Disease. Avian Pathology. 36, 5: 367-374.

- Steensels, M., Van Borm, S., Boschmans, M., Van Den Berg, T. (2007). Pathogenic and molecular characterisation of a HPAI H5N1 virus isolated from eagles smuggled from Thailand into Europe. Avian Diseases, 51:401-407.

- Steensels, M., Van Borm, S., Lambrecht, B., De Vriese, J., Legros, F., Bublot, M., Van Den Berg, T. (2007). Efficacy of an inactivated vaccine and a fowlpox recombinant in Muscovy ducks against an Asian HPAI H5N1 challenge. Avian Diseases 51: 325-331.

- Lambrecht, B., Van Borm, S., Steensels, M., van den Berg, T. (2007). Development of an M2e-specific ELISA for DIVA testing. Avian Diseases, 51: 221-226.

- Van Borm, S., M. Steensels, H. Ferreira, M. Boschmans, J. De Vriese, B. Lambrecht, T. van den Berg. (2007). A universal avian endogenous real time RT-PCR control and its application to avian influenza diagnosis and quantification. Avian Diseases. 51: 213-220.

- Rauw F., Lambrecht B., François A., Langlois P. & van den Berg T. (2007). Kinetic and biological properties of recombinant ChIFN expressed via CELO-virus vector. Journal of Interferon & Cytokine Research. 27(2): 111-118.

- Van den Berg T. (2006). Avian influenza: the ballad of influenza or the art of the fugue
- Bull Mem Acad R Med Belg. 161(5): 240-245.

- Steensels M, Van Borm S, van den Berg TP. (2006). Avian influenza: mini-review, European control measures and current situation in Asia. Verh K Acad Geneeskd Belg.; 68(2):103-120.

- Van Borm S, Thomas I, Hanquet G, Lambrecht B, Boschmans M, Dupont G, Decaestecker M., Snacken R. and van den Berg T. (2005). Highly pathogenic H5N1 influenza virus in smuggled eagles, Belgium. Emerging Infectious Diseases, 11, 5, 702-705.

- Dewulf J., Koenen F., De Clercq K., van den Berg T., Ribbens S. & De Kruif A. (2005). Uitbraken en bestrijding van Klassieke Varkenspest, Mond- en Klauwzeer en Hoge Pathogeen Aviaire Influenza in de Europese Unie. Vlaams Diergeneeskundige Tijdschrift, 74, 103-116.

- Suetens C, Snacken R, Hanquet G, Brochier B, Thomas I, Yane F, van den Berg T, Lambrecht B, Van Borm S. (2004). Eagles testing positive for H5N1 imported illegally into Europe from Thailand. Eurosurveillance, 8, 44.

- Saegerman C., Meulemans G., Van Reeth K., Marlier D., Yane F., Vindevogel H., Brochier B., van den Berg T., Thiry E. (2004). Evaluation, contrôle et prévention du risque de transmission du virus influenza aviaire à l'homme. Annales de Médecine Vétérinaires., 148 (2), 65-77.