1) In late 2014, outbreaks of highly pathogenic avian influenza (HPAI) H5N8 virus from the Gs/GD lineage first emerged in poultry and wild birds in Europe, Asia, and North America. 2) The H5N8 virus spread from migratory waterfowl through the Pacific Flyway in North America, infecting commercial and backyard flocks across 21 U.S. states. 3) Factors associated with farm-to-farm spread included common disposal of dead birds and garbage pickup, while most early cases resulted from introduction through wild birds.

1. IMPACT OF EMERGENCE OF AVIAN INFLUENZA IN NORTH
AMERICA AND PREVENTATIVE MEASURES
David E. Swayne, Kateri Bertran, Darrell Kapczynski, Mary Pantin-Jackwood, Erica Spackman,
Dong-Hun Lee and David L. Suarez
Southeast Poultry Research Laboratory,
U.S. National Poultry Research Center, Agricultural Research Service,
U.S. Department of Agriculture,
934 College Station Road, Athens, Georgia 30605 USA
ABSTRACT
Since 1959,40 epizootics of high pathogenicity avian influenza (HPAI) have occurred with the majority
using stamping-out programs leading to rapid eradication. The H5 Goose/Guangdong (Gs/GD)-lineage
HPAI, which originated in China in 1996, has been the largest epizootic; causing deaths in wild birds,
poultry and humansin 70 countries in Asia, Europe and Africa, and recently in North America. Endemic
infections occur in poultry in some Asian and African countries. In late 2014, outbreaks of H5N8 HPAI
(clade 2.3.4.4 Gs/GD lineage) were reported in several European Union countries, Korea and Japan.
Beginning in December2014, the Canada and USA have experienced outbreak of H5N8,and reassortant
H5Nx, Gs/GD-lineage HPAI. Subsequently, the H5Nx HPAI viruses spread through the Pacific Flyway
and to the Midwest USA. Molecular analysis indicated that the infected premises (backyard and
commercial) in Western and initial premisesin Midwestern USA were point source introductions from
wild birds, while most cases in the Midwest had secondary spread from common sources. This
emphasizes the need for improved biosecurity to prevent introduction of HPAI viruses and rapid
stamping-out response for eradication. Vaccination has been used to manage outbreaksin some countries
but not to-date in USA.
INTRODUCTION
The first cases of HPAI, previously termed fowl plague, were reported in 1878 in northern Italy, followed
by widely dispersed geographic outbreaks throughout the late 1800’s to 1950’s in Europe, Asia, Africa,
and North and South America. In general since 1959, HPAI outbreaks have been more geographically
restricted with 40 distinct HPAI epizootics. Such HPAI viruses have arisen from H5 or H7 low
pathogenicity avian influenza (LPAI), which the latter are non-pathogenic flora in some migratory
waterfowl and shorebirds. These LPAI viruses after exposure, adaptation and circulation in gallinaceous
poultry developed specific mutations in the hemagglutinin protein that conferred phenotypic traits of high
pathogenicity. Most of these epizootic HPAI viruses were geographically-limited, involved farm-to-farm
spread and were eradicated from poultry by stamping-out programs; i.e. the HPAI viruses did not
circulate in wild migratory birds. However, an H5N1 HPAI virus emerged in 1996 in a goose in
Guangdong China (Gs/GD lineage), and unlike the viruses in the other 39 HPAI outbreaks, has caused
deaths in wild birds, poultry and humans, and spread to over 70 countries in Asia, Europe, Africa and
North America; drastically changing the perspective on HPAI biology. The severity, size and broad
geographic distribution of Gs/GD epizootic merits the term panzootic.

2. HPAI NORTH AMERICA, 2014-2015
Between December 2014 and June 2015, Canada and USA experienced an unpreceded outbreak of H5
Gs/GD-lineage HPAI as the first intercontinental spread of a Eurasian HPAI virus to North America.
Initially, a reassortant H5N2 clade 2.3.4.4 HPAI virus was identified in British Columbia, Canada, and
within a few days the original Eurasian H5N8 and a Eurasian-North American reassortant and variant
H5N2 HPAI viruses were isolated from a gyrfalcon and a wild duck in Washington State, respectively.
This H5N8 HPAI virus was spread by migratory waterfowl from Eastern Asia to Russia, Europe and
North America (2,4). In North America, the Asian H5N8 HPAI virus reassorted with North America
LPAI virus genes to produce H5N2 and H5N1 HPAI viruses (1,3). Subsequently, the H5 HPAI viruses
spread through the Pacific Flyway and to the Midwest USA.
Molecular analysis indicated that the infected premises (backyard and commercial) in Western USA
and initial premises in Midwestern USA were point source introductions from wild birds, while most
cases in the Midwest had secondary spread from common sources; i.e. linkages between Midwest farms.
In total, the H5 HPAI outbreaks has affected 21 states, with detections in 4 captive wild birds, 75 wild
birds, 21 backyard flocks and 211 commercial flocks, totaling over 48 million birds. In the USA, the
eradication effort cost more than $1 billion and the negative economic impact was over $3.2 billion.
In the Midwest USA,specific risk factors were identified in association with farm-to-farm spread and
a minority of cases were consistent with airborne dispersion
(https://www.aphis.usda.gov/animal_health/animal_dis_spec/poultry/downloads/Epidemiologic-Analysis-
Sept-2015.pdf). Risk factors associated with introduction included being in a control zone, using a
common renderer for on farm dead bird pick-up, and common garbage pick-up on farm.
TRADE ISSUES
HPAI can be used as a non-tariff trade barrier to prevent introduction into an HPAI-free country, but the
risk of introduction through trade varies with commodity. Importation of live birds are the highest risk
while importation of cooked products are the lowest risk for HPAI virus introduction. The surveillance
data and risk analysis used to ensure freedom from HPAI, and thus low risk for trade, must take into
account several variables: 1) the extent of coverage such as whole country, a defined geographic zone or a
management compartment; 2) the number of samples and number of farms/premises tested for a specific
prevalence rate, 3) sensitivity and specificity of the surveillance test methodology, and 4) stage of
infection as either active viral infections or antibodies indicating a history of infections which may be
over. All results should be reported transparently to the World Organization for Animal Health and
trading partners.
PREVENTATIVE MEASURES
Improvements have been made to HPAI response in USA based on lessons learned from 2014-2015
outbreak and include redevelopment of an H5 vaccine bank, commitment to a timeline of 24 hours from
diagnosis to depopulation, and refocusing to rapid disposal methods with composting preferred and
landfill as secondary method.
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