Avian influenza overview February – May 2020

Abstract

Between 16 February and 15 May 2020, 290highly pathogenic avian influenza (HPAI) A(H5) virus outbreakswere reported in Europe in poultry (n=287), captive birds (n=2) and wild birds (n=1)in Bulgaria, Czechia,Germany,Hungary andPolandand two low pathogenic avian influenza (LPAI) A(H7N1) virus outbreaks were reported in poultry in Italy. 258 of 287 poultry outbreaks detected in Europe were secondary outbreaks, suggesting that in the large majoryty of cases the spread of the virus was not due to wild birds.Allthe HPAI outbreaks were A(H5N8) apart from three,which were reported as A(H5N2) from Bulgaria. Genetic analysis of the HPAI A(H5N8) viruses isolated from the eastern and central European countries indicates that this is a reassortant between HPAI A(H5N8) viruses from Africa and LPAI viruses from Eurasia. Two distict subtypes were identified in Bulgaria, a novel reassortant A(H5N2) and A(H5N8) that is persisting in the country since 2016. There could be several reasons why only very few HPAI cases were detected in wild birds in this 2019‐2020 epidemic season and a better knowledge of wild bird movements and virus‐host interaction (e.g. susceptibility of the hosts to this virus) could help to understand the reasons for poor detection of HPAI infected wild birds. In comparison with the last reporting period, a decreasing number of HPAI A(H5)‐affected countries and outbreaks were reported from outside Europe. However, there is considerable uncertainty regarding the current epidemiological situation in many countries out of Europe. Four human cases due to A(H9N2) virus infection were reported during the reporting period from China.

Antibodies to Highly Pathogenic A/H5Nx (Clade 2.3.4.4) Influenza Viruses in the Sera of Vietnamese Residents

“…Regardless of the evolutionary way in which these reassortants emerged, it is known that all of them caused infectious diseases among humans [ 14 , 15 , 16 ]. Since 2014, H5N6 viruses (2.3.4.4) have caused 27 human infections, resulting in 15 deaths in China [ 20 ]. Most human cases are associated with A or B reassortants.…”

Emergence and spread of novel H5N8, H5N5 and H5N1 clade 2.3.4.4 highly pathogenic avian influenza in 2020

“…The emergence of these clade 2.3.4.4b H5 viruses in Eurasia has significant implications for the poultry sector across Europe, Central Asia, The Middle East and Africa during winter 2020–2021 [ 7 ]. An alert has already been raised for increased vigilance across northern and eastern Europe based on historic outbreaks in Russia and subsequent spread of disease in both 2005 and 2016 [ 8 , 9 ]. The heterogeneity already detected in these emergent viruses poses significant challenges in assessing host tropism, pathogenesis, routes of transmission and disease dispersal and above all defining efficacious risk mitigation strategies.…”

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

“…Viruses 2021, 13, 2086 2 of 11 In December 2019 a new incursion of a HPAI H5N8 subtype was reported in Poland [4]. Since then, the virus has spread to 8 central-eastern European countries (Bulgaria, Czech Republic, Germany, Hungary, Poland, Romania, Slovakia, Ukraine), affecting mainly the poultry population, with more than 300 outbreaks notified in Hungary and Poland [5][6][7][8]. The last outbreak was reported in June 2020.…”