Novel Reassortant Influenza A(H5N8) Viruses, South Korea, 2014

To the Editor: Highly pathogenic avian influenza (HPAI) viruses have caused considerable economic losses to the poultry industry and poses potential threats to animal and human health Since 2003, influenza A(H5N1) viruses with a hemagglutinin (HA) gene derived from A/goose/Guandong/1/96–like viruses have become endemic to 6 countries (Bangladesh, China, Egypt, India, Indonesia, and Vietnam) (1) (www.cdc. gov/). Furthermore, HPAI viruses with an H5 subtype continue to undergo substantial evolution because of extensive genetic divergence and reassortment between other subtypes of influenza viruses. Especially in China, novel subtypes of H5 HPAI virus, such as influenza A(H5N2), influenza A(H5N5), and influenza A(H5N8) viruses, were reported signs of HPAI, such as decreased egg production (60%) and slightly increased mortality rates, were detected in ducks on a breeder duck farm near the Donglim Reservoir in Jeonbuk Province, South Korea. On January 17, a farmer (5 km from the Donglim Reservoir) also reported clinical signs of HPAI in broiler ducks. In addition, 100 carcasses of Baikal teals were found in the Donglim Reservoir. RNAs extracted from organs (liver , pancreas, and trachea) of 3 dead birds (1 breeder duck, 1 broiler duck, and 1 Baikal teal) were positive for H5 subtype virus by reverse transcription PCR (4). We isolated viruses from suspected specimens by inoculation into embryonated specific pathogen– free chicken eggs. The H5N8 subtype was identified by using HA and neur-aminidase (NA) inhibition assays. Three viruses isolated from domestic ducks and wild birds were designated A/breeder duck/Korea/ Gochang1/2014 (H5N8) (Gochang1), A/duck/Korea/Buan2/2014 (H5N8) (Buan2), and A/Baikal Teal/Korea/ Donglim3/2014 (H5N8) (Donglim3). All 8 RNA genome segments of these viruses were amplified by using segment specific primers and directly se-quenced (5). Sequences of the 8 RNA segments of each virus were submitted to GenBank under accession nos. KJ413831–KJ413854. Gochang1 virus has been shown to be highly pathogenic for chickens (intravenous pathogenicity index 3.0) (6). This finding was consistent with analysis of the HA gene, as shown by a series of deduced basic amino acid sequences (Gochang1, LREKRRKR/ GLF, Buan2 and Donglim3, LR-ERRRKR/GLF) at cleavage sites of HA (6). This outbreak of influenza A(H5N8) infection in South Korea was reported to the World Organisation for Animal Health (7). Nucleotide identity analysis with BioEdit version 7.2.5 showed that 3 distinct novel influenza A(H5N8) viruses emerged in South Korea. Gochang1 virus had 87%–97% sequence identities in the 8 genome segments with sequences for Buan2 and Donglim3 viruses, which had high …