NRL of Influenza and Acute Respiratory Diseases

Head of NRL Influenza and Acute Respiratory Diseases

Prof. Neli Korsun, MD, DSc

1233 Sofia, Bulgaria; 44A General Stoletov blvd.

tel. 02 / 931 81 32

email:This email address is being protected from spambots. You need JavaScript enabled to view it.

Laboratory staff:

  • Ivelina Trifonova, PhD, Assist. Prof.

  • Veselin Dobrinov, PhD, Assist. Prof.

  • Iliyana Grigorova - biologist

  • Iveta Madzharova – biologist

  • Yordanka Dobrinova - biologist

  • Iva Boncheva – lab. worker

 

History of laboratory

The National Reference Laboratory "Influenza and ARD" has a leading role in tracking the circulation of influenza viruses and deciphering the etiology of influenza epidemics in the country. In the laboratory, an effective influenza research scheme has been implemented, including a WHO-recommended complex of classical and modern methods, and applicable both during seasonal influenza epidemics and when a new pandemic influenza virus appears. In addition to traditional virus isolation and typing methods, modern laboratory techniques are applied, directly detecting viral nucleic acids (PCR) and specific antibodies (ELISA). A leading diagnostic method for the detecting, typing, and subtyping of influenza viruses is Real-Time RT-PCR, which is performed according to a WHO-recommended protocol, with primers and probes obtained from the Centers for Disease Control (CDC) in Atlanta, USA.

Using the Real-Time PCR method, other respiratory viruses - respiratory syncytial virus (RSV), metapneumovirus, parainfluenza, adeno-, rhino-, boca-and coronaviruses, including the Middle East respiratory syndrome coronavirus (MERS-CoV), are also detected.

Since February 2020, the laboratory has been performing SARS-CoV-2 diagnostics using the Real Time RT-PCR method. As part of the WHO system since 1960, of the European Scientific Scheme (EISS) - since 2007, and of the European Center for Disease Control (ECDC) - since 2009, the laboratory is included in the European and global exchange network of data regarding influenza, SARS-CoV-2, and other respiratory infections. The laboratory is recognized by the WHO as a National Influenza Center.

The employees of the laboratory conduct various forms of postgraduate training for specialists from the country; prepare methodological guidelines for the diagnosis of influenza and acute respiratory infections. The quality of laboratory diagnostics is proven annually through participation in several international external assessment programs organized by WHO, INSTAND Homepage - Germany, and ECDC.

Important publications:

  1. Korsun N, Trifonova I, Dobrinov V, Madzharova I, Grigorova I, Christova I. Low prevalence of influenza viruses and predominance of A(H3N2) virus with respect to SARS-CoV-2 during the 2021-2022 season in Bulgaria. J Med Virol. 2023;95:
  2. Trifonova I, Christova I, Madzharova I, Angelova S, Voleva S, Yordanova R, Tcherveniakova T, Krumova S, Korsun N. Clinical significance and role of coinfections with respiratory pathogens among individuals with confirmed severe acute respiratory syndrome coronavirus-2 infection. Front Public Health.2022;10:959319.
  3. Alexiev I, Giovanetti M, Cella E, Ivanov I, Stoikov I, Donchev D, Grigorova L, Gancheva A, Dimitrova R, Korsun N, Trifonova I, Philipova I, Dobrinov V, Grigorova I, Kantardjiev T, Christova I, Ciccozzi M. Initial introduction and spread of the SARS-CoV-2 AY.4.2.1 Delta variant in Bulgaria, a genomic insight. J Med Virol. 2022,94(12):6060-6064.
  4. Mileva S, Ivanova-Todorova E, Tumagelova-Yuzeir K, Trifonova IT, Korsun NS, Alexiev VA. Periostin and IFN-γ levels in serum and nasopharyngeal aspirate in infants with viral-induced wheezing - 2 year follow-up. Turk J Pediatr. 2022;64(6):1021-1030.
  5. Alexiev I, Ivanov I, Philipova I, Korsun N, Stoikov I, Dimitrova R, Grigorova L, Gancheva A, Trifonova I, Dobrinov V, Grigorova I, Savov A, Asenova B, Ciccozzi M, Kantardjiev T. Postvaccination SARS-CoV-2 Alpha (B.1.1.7) lineage infection among healthcare workers on the background of IgG antibodies. J Med Virol. 2021, 94(3):836-839.
  6. Korsun N, Angelova S, Trifonova I, Voleva V, Grigorova I, Tzotcheva I, Mileva S, Alexiev I, Perenovska P. Predominance of ON1 and BA9 genotypes of Respiratory Syncytial Virus in Bulgaria, 2016-2018. J Med Virol. 2021, 93(6):3401-3411.
  7. Korsun N, Trifonova I, Voleva S, Grigorova I, Angelova S. Genetic characterisation of the influenza viruses circulating in Bulgaria during the 2019-2020 winter season. Virus Genes. 2021;57(5):401-412.
  8. Korsun NS, Angelova SG, Trifonova IT, Voleva SE, Grigorova IG, Tzotcheva IS, Mileva SD, Perenovska PI. The Prevalence and Genetic Characterization of Human Metapneumovirus in Bulgaria, 2016-2019. 2021;64(4):194-202.
  9. Korsun N, Angelova S, Trifonova I, Georgieva I, Voleva S, Grigorova I, Tzotcheva I, Mileva S, Perenovska. P. Prevalence and genetic characteristics of human bocaviruses detected in patients with acute respiratory infections in Bulgaria. Int J Microbiol, 2021:7035081.
  10. Korsun N, Trifonova I, Dobrinov V, Grigorova I, Angelova S, Alexiev I. SARS-CoV-2: Insight into the emerging genetic variants. Probl Infect Parasit Dis, 2021, 49(3):5-11.
  11. Korsun N, Daniels R, Angelova S, Ermetal B, Grigorova I, Voleva S, Trifonova I, Kurchatova A, McCauley J. J Genetic diversity of influenza A viruses circulating in Bulgaria during the 2018-2019 winter season. J Med Microbiol. 2020, 69(7):986-998.
  12. Korsun N, Angelova S, Trifonova I, Georgieva I, Voleva S. Viral respiratory pathogens associated with medically attended acute respiratory illnesses in older adults in Bulgaria. Comptes rendus de l’Académie bulgare des Sciences, 2020, 73 (4), 490-497.
  13. Korsun N.S., Angelova S.G., Trifonova I.T., Georgieva I.L., Tzotcheva I.S., Mileva S.D., Voleva S.E., Kurchatova A.M., Perenovska P.I. Predominance of influenza B/Yamagata lineage viruses in Bulgaria during the 2017/2018 season. Epidemiol Infect 2019,147:e76.
  14. Korsun N, Angelova S, Trifonova I, Georgieva I, Voleva S, Tzotcheva I, Mileva S, Ivanov I, Tcherveniakova T, Perenovska P. Viral pathogens associated with acute lower respiratory tract infections in children younger than 5 years of age in Bulgaria. Braz J Microbiol, 2019;50(1):117-125.
  15. Georgieva B, Gergova R, Perenovska P, Miteva D, Parina S, Korsun N, Setchanova L, Petrova G. Infectious Pathogens that Could Trigger Cough in Children Outside Winter Epidemic Season. Annals of Microbiology and Infectious Diseases. 2019, 2(1):52-57
  16. Pekova L, Parousheva P, Tzoneva V, Naydenov K, Mitev M, Petrov D, Angelova S, Korsun N. Influenza-Associated Neurological Complications - Clinical Course and Prognostic Factors. Vaccines Vacccin 2018, 3(2): 000124.
  17. Korsun N, Angelova S, Trifonova I, Tzotcheva I, Mileva S, Voleva S, Georgieva I, Perenovska P. Predominance of influenza A(H3N2) viruses during the 2016/2017 season in Bulgaria. J Med Microbiol. 2018;67(2):228-239.
  18. Korsun N, Angelova S, Tzotcheva I, Georgieva I, Lazova S, Parina S, Alexiev I, Perenovska P. Prevalence and genetic characterisation of respiratory syncytial viruses circulating in Bulgaria during the 2014/15 and 2015/16 winter seasons. Pathog Glob Health. 2017;111(7):351-361.
  19. Korsun N, Angelova S, Gregory V, Daniels R, Georgieva I, McCauley J. Antigenic and genetic characterization of influenza viruses circulating in Bulgaria during the 2015/2016 season. Infect Genet Evol. 2017, 49:241-250.
  20. Korsun N, Angelova S, Teodosieva A. Virological Surveillance of Influenza in Four Recent Post-Pandemic Seasons (2010/11 to 2013/14) in Bulgaria. Cent Eur J Public Health. 2016, 24(3):180-187.
  21. Beauté J., P.Zucs, N. Korsun, K. Bragstad, V. Enouf, A. Kossyvakis, A.Griškevičius, C. M. Olinger, A. Meijer, R. Guiomar, K. Prosenc, E. Staroňová, C. Delgado, M. Brytting, E. Broberg. Age-specific differences in influenza virus type and subtype distribution in the 2012/2013 season in 12 European countries. Epidemiol Infect. 2015 Feb 4:1-9.
  22. Korsun N., A. Teodosieva, S. Angelova. Etiological role of ortho- and paramyxoviruses in acute respiratory tract infections among children aged < 4 years in Bulgaria. Lab, 2015, 61, 3+4:219-226.
  23. Angelova S. G., I. L. Georgieva, A.A. Teodosieva, N. S. Korsun. Neuraminidase inhibitor susceptibility of influenza viruses circulating in Bulgaria during the last four consecutive epidemic seasons (2011/12 to 2014/15). American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS), 2015, 12 (1):162-169.
  24. Korsun N., S. Angelova, I. Georgieva. Influenza virus activity during the 2013/2014 and 2014/2015 seasons in Bulgaria. Comptes rendus de l’Acade'mie bulgare des Sciences, 2015, 68 (9)
  25. Korsun N., A.Teodosieva, M. Jordanova. Influenza Virus Activity During the 2011/2012 and 2012/2013 Seasons in Bulgaria. Comptes rendus de l’Acade'mie bulgare des Sciences, 2014, 67, 2, 277-282.
  26. Trifonova I, Angelova S, Korsun N. Aetiologic structure of acute respiratory tract infections among children younger than 5 years in Bulgaria. Probl Infect Parasit Dis, 2019, 47 (1):9-15.
  27. Лазова Сн, Цочева И, Корсун Н, Паринa Сн, Ангелова Св, Трифонова Ив, Георгиевa Б, Еленчева Е, Переновска П. Клинично протичане на инфлуенца вирусна инфекция и асоциирана с грип пневмония при деца над 2-годишна възраст, сезон 2017/2018. Детски и инфекциозни болести, 2019, 11 (1), 19-24.
  28. Иванов И, Пачева И, Панова М, Габерова Г, Янков И, Чочакова Л, Стоев И, Маркова П, Драгнева В, Ниева И, Маринска В, Гечев Н, Петрова А, Троянчева М, Ангелова С, Корсун Н, Стойчева М, Мангъров А, Литвиненко И, Шмилев Т. Енцефалопатии свързани с вирусна инфекция - 5 годишен опит в педиатрично отделение. Педиатрия, 2018,58(1):47-51.
  29. Корсун Н., Св. Ангелова, И. Георгиева. И. Трифонова, С. Волева. Квадривалентни противогрипни ваксини - нова възможност за превенция и контрол на грипа. Наука. Пулмология, 2017, 4: 26-29.
  30. Корсун Н., Св. Ангелова, И. Георгиева. Респираторно-синцитиалният вирус - главен респираторен патоген в педиатричната практика. Наука Пулмология, 2016, 1, 16-19.
  31. Ангелова Св., И. Георгиева, Н. Корсун. Проучване участието на 15 респираторни вируса в етиологията на острите респираторни заболявания при деца на възраст под 5 год. в България. Педиатрия, 2015, 3, 26- 29.
  32. Ангелова А., А. Теодосиева, И. Иванов, Н. Корсун. Вирусна етиология на острите респираторни заболявания през сезони 2012/2013 г. и 2013/2014 г. в България. Наука Инфектология. Паразитология, 2015, 1, 32-36.
  33. Georgieva I., S. Angelova, N. Korsun. Viral etiology of acute respiratory infections among children under 5 years of age in Bulgaria, during the 2013/2014 and 2014/2015 seasons. Trakia J of Sciences, 2015, 13, Suppl.2: 55-60.
  34. Teodosieva A., S. Angelova, N. Korsun. Infections with influenza viruses, respiratory-syncytial virus and human metapneumovirus among hospitalized children aged ≤ 3 years in Bulgaria. Trakia J of Sciences, 2014, 12, Suppl.1: 226-232.
  35. Иванов И., С. Ангелова, А. Теодосиева, М. Йорданова, А. Мангъров, Т. Червенякова, Н. Корсун. Вирусологично и клинично проучване на хоспитализирани пациенти с грипоподобни заболявания през сезон 2013/2014 г. Наука Инфектология. Паразитология, 2014, 2, 23-25.
  36. Корсун Н., А. Теодосиева, М. Йорданова, А. Курчатова, М. Кожухарова. Грипен сезон 2012/2013 г. – вирусологични и епидемиологични аспекти. Бълг. мед. журнал, 2014, 1, 55-60.
  37. Корсун Н., С. Ангелова, А. Теодосиева, М. Йорданова. Пандемичен риск, свързан с нововъзникнали респираторни вирусни инфекции. Наука Инфектология. Паразитология, 2014, 1, 4-7.
  38. Корсун Н., А. Теодосиева. Резистентност на грипните вируси към антивирусни препарати. Наука. Инфектология. Паразитология, 2013, 2.
  39. Korsun N., A. Teodosieva, M. Jordanova. Neuraminidase inhibitors susceptibility testing of influenza viruses circulating in Bulgaria during the first three postpandemic flu seasons. Probl Infect Par Dis, 2012, 40 (2): 25-28.
  40. Корсун Н., Р. Коцева. Инфекция с РСВ при деца, хоспитализирани с бронхиолит и пневмония през сезон 2010/2011г. Педиатрия, 2012, 3, 46-48.
  41. Корсун Н., Р. Коцева, А.Теодосиева, А.Курчатова, П. Генова-Калу, М. Кожухарова. Особености на грипните епидемии в България през първите два сезона от постпандемичния период. Бълг. мед. журнал, 2012, 2: 31-37.