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**SCREENING FOR HIGHLY PATHOGENIC H5N1 AVIAN INFLUENZA IN MIGRATORY
BIRDS**

"An Early Detection System for H5N1 Highly Pathogenic Avian Influenza in
Wild Migratory Birds \-- U.S. Interagency Strategic Plan"

March 2006

Avian influenza (AI) is a virus that is naturally found in wild birds,
particularly in certain species of waterfowl and shorebirds. Occurrences
of an H5N1 highly pathogenic avian influenza (HPAI) virus overseas have
heightened concern regarding the potential impact on wild birds,
domestic poultry and human health should it be introduced into the
United States.

To understand the differences and potential threats to U.S. bird
populations, this fact sheet provides definitions, a historical
perspective and an outline of the U.S. Department of Agriculture (USDA)
and U.S. Department of the Interior (DOI) efforts to detect the H5N1
HPAI virus in wild migratory birds.

BACKGROUND

ABOUT THE VIRUS

AI viruses are classified by a combination of two groups of proteins
found on the surface of the virus: hemagglutinin proteins (H), of which
there are 16 (H1-H16), and neuraminidase proteins (N), of which there
are 9 (N1-N9). There are 144 possible combinations or subtypes based
upon this classification scheme.

Wild birds, in particular certain species of waterfowl and shorebirds,
are considered to be the natural reservoirs for avian influenza viruses.
These subtypes that naturally occur in wild species usually cause little
or no disease. However, domestic birds are generally more susceptible to
avian influenza virus and mutation or recombination of a virus acquired
from wild birds can increase its disease potential in these domestic
birds.

AI strains also are divided into two groups based on the pathogenicity
of the virus\--the ability of the virus to produce disease.

**Low Pathogenicity Avian Influenza (LPAI):** Most AI strains are
classified as low pathogenicity and cause few clinical signs in infected
birds. LPAI generally does not pose a significant health threat to
humans. However, LPAI is monitored because two strains of LPAI---the H5
and H7 strains--can mutate into highly pathogenic forms.

**High Pathogenicity Avian Influenza (HPAI):** This type of avian
influenza is frequently fatal to birds and easily transmissible between
susceptible species. The strain that is currently of concern in Asia,
Europe, the Middle East and Africa is the H5N1 HPAI virus.

[TIMELINE]{.underline}

Since 1997 when it first appeared in Hong Kong, federal wildlife experts
and public health officials have been monitoring the spread of the
highly pathogenic H5N1 virus**.**

Since 1998, USDA, in partnership with the University of Alaska, has
tested over 12,000 wild migratory birds in the Alaska flyway and almost
4,000 wild migratory birds in the Atlantic flyway. All birds have tested
negative for the highly pathogenic H5N1 virus.

DOI and USDA stepped up wild bird monitoring and testing programs when
the highly pathogenic H5N1 virus spread throughout Southeast Asia and
Russia.

Since summer 2005, DOI biologists have been working with the State of
Alaska to sample migratory birds for H5N1 in the Pacific Flyway. DOI has
tested more than 1,700 samples from more than 1,100 migratory birds.
There have been 22 avian influenza isolates identified, but none have
been highly pathogenic.

In August 2005, as part of the President's National Strategy for
Pandemic Influenza Preparedness, the USDA and DOI convened a joint
working group with the U.S. Department of Health and Human Services
(HHS), State of Alaska and the International Association of Fish and
Wildlife Agencies to develop a national strategic plan for early
detection of H5N1 HPAI should it be introduced into North America by
wild birds.

[THE WILD BIRD PLAN]{.underline}

PLAN OVERVIEW

The interagency strategic plan, developed by wildlife disease
biologists, veterinarians and epidemiologists, provides a unified
national system for conducting H5N1 HPAI monitoring of wild migratory
birds throughout the United States. The plan serves as a guide to all
federal, state, university and non-governmental organizations involved
in avian influenza monitoring by providing standard procedures and
strategies for data sampling, diagnostics, and management.

FIVE STRATEGIES OF THE PLAN

The plan targets bird species in North America that have the highest
risk of being exposed to or infected with highly pathogenic H5N1 because
of their migratory movement patterns. Key species of interest include
ducks, geese, and shorebirds.

If wild birds are or become able to effectively move the disease over
great distances, scientists believe introduction of H5N1 into the United
States would most likely occur in Alaska, where there is significant
mixing of Asian and North American birds. Therefore, the interagency
strategic plan recommends a prioritized sampling system with emphasis
first in Alaska, the Pacific Flyway and Pacific Islands, followed by the
Central Flyway, Mississippi Flyway and Atlantic Flyway. The five
strategies are:

1.  **Investigation of morbidity/mortality in wild birds**: The
    systematic investigation of significant numbers of sick or dead
    birds offers the highest and earliest probability of detection, if
    the highly pathogenic H5N1 virus is introduced into the United
    States by migratory birds. Biologists and veterinarians in state and
    federal wildlife and natural resource agencies and animal health
    agencies and organizations, are prepared to detect and respond to
    such discoveries. In the event that a highly pathogenic H5N1 is
    detected in wild birds, USDA will identify and monitor domestic
    poultry and swine operations in the area and minimize contact
    between the wild birds and domestic animals.

2.  **Monitoring live, apparently healthy wild birds:** This effort
    targets wild birds in North America that represent the highest risk
    of being infected with highly pathogenic H5N1 avian influenza,
    because of their migratory movement patterns. Species that will be
    sampled include birds that migrate directly between Asia, Oceania
    (including Hawaii, U.S. Pacific Territories and Freely Associated
    States) and North America, and birds that might be in contact with
    species from areas in Asia with reported avian influenza outbreaks.
    This includes sampling live-captured, apparently healthy wild birds
    to detect the presence of highly pathogenic H5N1 virus. Data
    collected in Alaska will be combined with data from additional bird
    captures to provide a broad species and geographic monitoring
    effort. In 2006, DOI, USDA and their cooperators plan to collect
    75,000 to 100,000 samples from live and dead wild birds.

3.  **Monitoring hunter-killed birds:** Hunter check stations operated
    by the FWS and state natural resource agencies for waterfowl hunting
    provide an opportunity to collect additional samples to test for the
    presence of highly pathogenic H5N1 and other subtypes of avian
    influenza. These samples supplement the targeted monitoring samples
    from live wild birds and focus on species that are most likely to
    have been exposed to highly pathogenic H5N1 viruses in Asia; have
    relatively direct migratory pathways from those areas to the United
    States via Alaska or directly to the Pacific Coast; or that mix in
    migratory staging areas in Alaska with species that could bring the
    virus from Asia. Collection of samples from these species will occur
    at hunter check stations in the lower 48 states, as well as Alaska,
    during hunting seasons in areas where these birds gather during
    migration or over-wintering. Samples also will be collected from
    wild birds taken by native Alaskans during the spring subsistence
    hunt. USGS, FWS and USDA are working with the four Migratory Bird
    Flyway Councils to enhance sampling plans for hunter-killed birds.

4.  **Use of sentinel animals:** There are two groups of animals used as
    sentinels in avian influenza monitoring programs that could provide
    early detection of the highly pathogenic H5N1 virus along migratory
    flyways in the United States. Poultry flocks reared in backyards
    (raised for noncommercial purposes) have been evaluated for diseases
    of interest to nearby commercial poultry operators as a monitoring
    method. Also, duck flocks can be placed in wetland environments
    where they may commingle with wild birds. The ducks are then
    monitored and tested for avian influenza viruses.

5.  **Environmental sampling of water and bird feces:** Waterfowl
    release avian influenza viruses through the intestinal tract and the
    virus can be detected in both feces and water in which the birds
    swim. This provides a means of virus spread to new avian hosts and
    potentially to poultry or other livestock. Analysis of both water
    and fecal material from waterfowl habitat can provide evidence of
    avian influenza circulating in wild bird populations. In 2006, USDA
    and others plan to collect 50,000 samples from high-risk waterfowl
    habitats across the United States.

**BENEFITS OF MONITORING DATA**

In addition to providing an early warning system for disease occurrence
in U.S. wild birds and domestic poultry, the monitoring data will be
used to create a national database that incorporates and tracks all
avian influenza data collected from wild birds in the United States. The
database will be available to all agencies, organizations and
policymakers involved in avian influenza monitoring and response. The
data collected in this system will be used by scientists to develop a
better understanding of the movement of avian influenza viruses among
wild and domestic animals, improve risk analyses and target monitoring
strategies to track regarding future avian influenza spread.

**Additional information**

For more information about avian influenza:

[www.usda.gov/birdflu](http://www.usda.gov/birdflu)

[www.nwhc.usgs.gov/research/avian_influenza/avian_influenza.html](http://www.nwhc.usgs.gov/research/avian_influenza/avian_influenza.html)

[www.pandemicflu.gov](http://www.pandemicflu.gov/)