First European detection of H9N2 clade G5.5 reported in Hungarian broiler farms

The latest avian influenza monitoring report published by the European Food Safety Authority (EFSA), the European Centre for Disease Prevention and Control (ECDC) and the European Union Reference Laboratory for Avian Influenza (EURL) documents the first detection in Europe of low pathogenic avian influenza (LPAI) H9N2 virus belonging to clade G5.5.

The virus was detected in April 2026 in seven establishments keeping broiler chickens located within the same geographical area in Hungary. Increased mortality in one establishment initially raised suspicions of highly pathogenic avian influenza (HPAI). After laboratory tests ruled out H5 and H7 viruses, further investigations identified H9N2 together with infectious bronchitis virus (IBV), with pathological findings consistent with a co-infection. The source of virus introduction could not be determined.

According to the report, all affected establishments were stamped out, cleaned and disinfected. Testing for H9N2 is planned two to three weeks after repopulation.

Genetic analysis showed that the Hungarian viruses belong to clade G5.5, a lineage that is endemic in domestic poultry in parts of Africa, the Middle East and West Asia but had never previously been detected in birds in Europe. The viruses also carry the HA-Q226L mutation, a marker associated with preferential binding to human-like α2-6-linked sialic acid receptors, as observed in most H9N2 viruses of this clade.

Although H9N2 is classified as a low pathogenic avian influenza virus, EFSA and ECDC note that clade G5.5 has previously been associated with sporadic human infections outside Europe. Because the origin of the Hungarian viruses remains unknown, EFSA and ECDC recommend continued surveillance to monitor any further spread of this lineage in European poultry populations.

Source: www.efsa.europa.eu

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