Gene

Infectivity

Pathology

Virology

Reassortment

Phylogenetic tree

Virus

Influenza A virus

Disease

Coronavirus disease 2019 (COVID-19)

Clade

Influenza A virus subtype H5N1

Infectious disease (medical specialty)

Genetics

Nucleoprotein

Medicine

H5N1 genetic structure

Biology

Phylogenetics

Epizootiology

Emerging infectious diseases

In 2016, an epidemic of highly pathogenic avian influenza A virus subtype H5N8 in the Netherlands caused mass deaths among wild birds, and several commercial poultry farms and captive bird holdings were affected. We performed complete genome sequencing to study the relationship between the wild bird and poultry viruses. Phylogenetic analysis showed that the viruses are related to H5 clade 2.3.4.4 viruses detected in Russia in May 2016 but contained novel polymerase basic 2 and nucleoprotein gene segments and 2 different variants of the polymerase acidic segment. Molecular dating suggests that the reassortment events most likely occurred in wild birds in Russia or Mongolia. Furthermore, 2 genetically distinct H5N5 reassortant viruses were detected in wild birds in the Netherlands. Our study provides evidence for fast and continuing reassortment of H5 clade 2.3.4.4 viruses, which might lead to rapid changes in virus characteristics, such as pathogenicity, infectivity, transmission, and zoonotic potential.

Multiple Reassorted Viruses as Cause of Highly Pathogenic Avian Influenza A(H5N8) Virus Epidemic, the Netherlands, 2016