Lessons from the Largest Epidemic of Avian Influenza Viruses in Taiwan, 2015.
The largest epidemic of avian influenza (AI) in history attacked poultry and wild birds throughout Taiwan starting January 6, 2015. This study analyzed surveillance results, epidemiologic characteristics, and viral sequences by using government-released information, with the intention to provide recommendations to minimize future pandemic influenza. The H5 clade 2.3.4.4 highly pathogenic AI viruses (HPAIVs) had not been detected in Taiwan before 2015. During this epidemic, four types of etiologic agents were identified: the three novel subtypes H5N2, H5N8, and H5N3 clade 2.3.4.4 HPAIVs and one endemic chicken H5N2 subtype (Mexican-like lineage) of low pathogenic AI viruses. Cocirculation of mixed subtypes also occurred, with H5N2 clade 2.3.4.4 HPAIVs accompanied by the H5N8 and H5N3 subtypes or old H5N2 viruses in the same farm. More than 90% of domestic geese died from this AI epidemic; geese were affected the most at the early outbreaks. The epidemic peaked in mid-January for all three novel H5 subtypes. Spatial epidemiology found that most affected areas were located in southwestern coastal areas. In terrestrial poultry (mostly chickens), different geographic distributions of AI virus subtypes were detected, with hot spots of H5N2 clade 2.3.4.4 vs. past-endemic old H5N2 viruses in Changhwa (P = 0.03) and Yunlin (P = 0.007) counties, respectively, of central Taiwan. Phylogenetic and sequence analyses of all the early 10 Taiwan H5 clade 2.3.4.4 isolates covering the three subtypes showed that they were very different from the HA of the past local H5 viruses from domestic ducks (75%-80%) and chickens (70%-75%). However, they had the highest sequence identity percentages (99.53%-100%), with the HA of A/crane/Kagoshima/KU13/2014(H5N8) isolated on December 7, 2014, in Japan being higher than those of recent American and Korean H5 HPAIVs [A/Northern pintail/Washington/40964/2014 (H5N2) and A/gyrfalcon/Washington/41088-6/2014 (H5N8): 99.02%-99.54% and A/Baikal teal/Korea/Donglim3/2014 (H5N8): 98.61%-99.08%], implying a likely common ancestor of these H5 clade 2.3.4.4 viruses. The multiple subtypes of H5 clade 2.3.4.4 HPAIVs imply high viral reassortment. We recommend establishing an integrated surveillance system, involving clinical, virologic, and serologic surveillance in poultry and wild birds, swine and other mammals prevalent on multiple-animal mixed-type traditional farms, and high-risk human populations, as a crucially important step to minimize future pandemic influenza.
A Institute of Biomedical Informatics, National Yang-Ming University, Taipei, Taiwan, Republic of China.
Ching-Fen
CF
Chang
B Institute of Epidemiology and Preventive Medicine, College of Public Health, National Taiwan University, Taipei, Taiwan (100), Republic of China.
Chwan-Chuen
CC
King
C Institute of Molecular & Comparative Pathobiology, School of Veterinary Medicine, National Taiwan University, Taipei, Taiwan (106), Republic of China.
Cho-Hua
CH
Wan
B Institute of Epidemiology and Preventive Medicine, College of Public Health, National Taiwan University, Taipei, Taiwan (100), Republic of China.
Yun-Cheng
YC
Chang
D Research Center for Humanities and Social Sciences, Academia Sinica, Taipei, Taiwan (115), Republic of China.
Ta-Chien
TC
Chan
B Institute of Epidemiology and Preventive Medicine, College of Public Health, National Taiwan University, Taipei, Taiwan (100), Republic of China.|E Genomics Research Center, Academia Sinica, Taipei, Taiwan (115), Republic of China.
Chang-Chun
CC
David Lee
B Institute of Epidemiology and Preventive Medicine, College of Public Health, National Taiwan University, Taipei, Taiwan (100), Republic of China.
Po-Hao Borris
PH
Chou
B Institute of Epidemiology and Preventive Medicine, College of Public Health, National Taiwan University, Taipei, Taiwan (100), Republic of China.
Zheng-Rong Tiger
ZR
Li
B Institute of Epidemiology and Preventive Medicine, College of Public Health, National Taiwan University, Taipei, Taiwan (100), Republic of China.
Yao-Tsun
YT
Li
B Institute of Epidemiology and Preventive Medicine, College of Public Health, National Taiwan University, Taipei, Taiwan (100), Republic of China.|F Department of Public Health, College of Medicine, Fu Jen Catholic University, New Taipei, Taiwan (242), Republic of China.
Tzu-Jung
TJ
Tseng
G Institute of Ecology and Evolutionary Biology, College of Life Sciences, National Taiwan University, Taipei, Taiwan (106), Republic of China.
Pei-Fen
PF
Lee
A Institute of Biomedical Informatics, National Yang-Ming University, Taipei, Taiwan, Republic of China.
Chuan-Hsiung
CH
Chang
D000818:Animals; D000835:Animals, Wild / Q000821:virology; D002645:Chickens; D004196:Disease Outbreaks; D004372:Ducks; D005777:Geese; D009980:Influenza A virus / Q000145:classification / Q000235:genetics / Q000302:isolation & purification*; D005585:Influenza in Birds / Q000453:epidemiology* / Q000821:virology; D010802:Phylogeny; D011201:Poultry Diseases / Q000453:epidemiology* / Q000821:virology; D013624:Taiwan / Q000453:epidemiology
Taiwan; epidemiology; highly pathogenic avian influenza H5 virus; phylogenetic analysis; prevention and control policy; surveillance