Human infection with avian influenza A H6N1 virus: an epidemiological analysis.
BACKGROUND
Avian influenza A H6N1 virus is one of the most common viruses isolated from wild and domestic avian species, but human infection with this virus has not been previously reported. We report the clinical presentation, contact, and environmental investigations of a patient infected with this virus, and assess the origin and genetic characteristics of the isolated virus.


METHODS
A 20-year-old woman with an influenza-like illness presented to a hospital with shortness of breath in May, 2013. An unsubtyped influenza A virus was isolated from her throat-swab specimen and was transferred to the Taiwan Centres for Disease Control (CDC) for identification. The medical records were reviewed to assess the clinical presentation. We did a contact and environmental investigation and collected clinical specimens from the case and symptomatic contacts to test for influenza virus. The genomic sequences of the isolated virus were determined and characterised.


RESULTS
The unsubtyped influenza A virus was identified as the H6N1 subtype, based on sequences of the genes encoding haemagglutinin and neuraminidase. The source of infection was not established. Sequence analyses showed that this human isolate was highly homologous to chicken H6N1 viruses in Taiwan and had been generated through interclade reassortment. Notably, the virus had a G228S substitution in the haemagglutinin protein that might increase its affinity for the human α2-6 linked sialic acid receptor.


CONCLUSIONS
This is the first report of human infection with a wild avian influenza A H6N1 virus. A unique clade of H6N1 viruses with a G228S substitution of haemagglutinin have circulated persistently in poultry in Taiwan. These viruses continue to evolve and accumulate changes, increasing the potential risk of human-to-human transmission. Our report highlights the continuous need for preparedness for a pandemic of unpredictable and complex avian influenza.


BACKGROUND
Taiwan Centres for Disease Control.
Centres for Disease Control, Taipei, Taiwan; School of Medicine, National Yang-Ming University, Taipei, Taiwan.
Sung-Hsi
SH
Wei
Centres for Disease Control, Taipei, Taiwan.
Ji-Rong
JR
Yang
Centres for Disease Control, Taipei, Taiwan; School of Medical Laboratory Science and Biotechnology, Taipei Medical University, Taipei, Taiwan.
Ho-Sheng
HS
Wu
Nantou Christian Hospital, Changhua, Taiwan.
Ming-Chuan
MC
Chang
Changhua Christian Hospital, Changhua, Taiwan.
Jen-Shiou
JS
Lin
Changhua Christian Hospital, Changhua, Taiwan.
Chi-Yung
CY
Lin
Centres for Disease Control, Taipei, Taiwan.
Yu-Lun
YL
Liu
Centres for Disease Control, Taipei, Taiwan.
Yi-Chun
YC
Lo
Centres for Disease Control, Taipei, Taiwan.
Chin-Hui
CH
Yang
Centres for Disease Control, Taipei, Taiwan; School of Medicine, National Yang-Ming University, Taipei, Taiwan.
Jen-Hsiang
JH
Chuang
Centres for Disease Control, Taipei, Taiwan.
Min-Cheng
MC
Lin
Nantou Hospital, Nantou City, Taiwan.
Wen-Chen
WC
Chung
Nantou Hospital, Nantou City, Taiwan.
Chia-Hung
CH
Liao
Animal Health Research Institute, Council of Agriculture, New Taipei City, Taiwan.
Min-Shiuh
MS
Lee
Centres for Disease Control, Taipei, Taiwan.
Wan-Ting
WT
Huang
Centres for Disease Control, Taipei, Taiwan.
Pei-Jung
PJ
Chen
Centres for Disease Control, Taipei, Taiwan. Electronic address: mtliu@cdc.gov.tw.
Ming-Tsan
MT
Liu
Centres for Disease Control, Taipei, Taiwan; Department of Internal Medicine, National Defence Medical Centre, Taipei, Taiwan. Electronic address: fychang@cdc.gov.tw.
Feng-Yee
FY
Chang
D000818:Animals; D004279:DNA, Viral / Q000032:analysis*; D005260:Female; D006801:Humans; D009980:Influenza A virus / Q000235:genetics*; D005585:Influenza in Birds / Q000453:epidemiology / Q000821:virology*; D007251:Influenza, Human / Q000453:epidemiology / Q000821:virology*; D058873:Pandemics; D011200:Poultry; D060888:Real-Time Polymerase Chain Reaction; D013624:Taiwan / Q000453:epidemiology; D055815:Young Adult
D004279:DNA, Viral