Order Code RS21747
Updated November 10, 2005
CRS Report for Congress
Received through the CRS Web
Avian Influenza: Agricultural Issues
Jim Monke
Analyst in Agricultural Policy
Resources, Science, and Industry Division
Summary
Since the fall of 2003, a strain of highly pathogenic avian influenza (H5N1) has
spread throughout Asia, infecting mostly poultry but also a limited number of humans.
In recent months, the virus has spread into parts of Europe. Controlling avian flu in
poultry is seen as the best way to prevent a human pandemic from developing, by
reducing the number of animal hosts in which the virus may evolve.
Avian flu can be highly contagious in domestic poultry. Strict biosecurity measures
are practiced among commercial poultry farms and are encouraged by governments.
The economic effects of any avian influenza outbreak can be significant, especially
given international trade restrictions. This report will be updated as events warrant.
Status of Avian Influenza Outbreaks
In the United States. The highly pathogenic H5N1 strain of current global
concern has not reached the United States, neither in poultry nor humans. (This report
primarily addresses avian flu in poultry, although some human dimensions are discussed.)
The most recent cases in domestic poultry were in 2004, with three unrelated and less
pathogenic strains.
To reduce the possibility that H5N1 enters U.S. borders, the U.S. Department of
Agriculture (USDA) has blocked imports of poultry and poultry products from affected
countries. The Department of Homeland Security helps with enforcement through
Customs and Border Protection. Surveillance of migratory birds is increasing.1
In the Rest of the World. Since December 2003, as many as nine Asian countries
have had confirmed outbreaks or instances of H5N1 in poultry, including Vietnam,
Thailand, Indonesia, Cambodia, China and Hong Kong, South Korea, Malaysia, Laos, and
Japan. More recently, in the summer and fall of 2005, H5N1 spread westward and has
been confirmed in at least five new countries: Russia, Kazakhstan, Turkey, Romania, and
1 For domestic issues related to avian flu in poultry, see the U.S. Department of Agriculture
(USDA) at [http://www.aphis.usda.gov/lpa/issues/avian_influenza]. For background on human
issues, see the Centers for Disease Control (CDC) at [http://www.cdc.gov/flu/avian].
Congressional Research Service ˜ The Library of Congress

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Croatia. Wild birds seem to be one of the main carriers, but their role in spreading the
virus is not completely understood. The risk and likelihood of the virus spreading into
Africa and the Middle East is increasing. Other countries on migratory bird routes are
increasing surveillance efforts.
As the virus spreads, and becomes endemic in countries with low levels of veterinary
services or animal husbandry practices that harbor the virus, the chances increase that the
virus will evolve through mutation or reassortment into a strain that could be transmitted
easily between humans. Thus, many experts call for the swift and coordinated control of
avian flu in poultry as the best way to prevent a human pandemic from developing, by
reducing the number of animal hosts in which the virus may evolve.2
The situation in Asia is historically unprecedented and extremely challenging. The
United Nations Food and Agriculture Organization (FAO) estimates that over 130 million
birds have died or been culled in Asia. Some countries were reluctant to acknowledge the
disease for fear of economic consequences. In other countries, lack of compensation for
farmers whose flocks are destroyed has been a disincentive to report outbreaks early. In
some parts of Asia, about 80% of the poultry are produced in small backyard farms
scattered throughout rural areas, further complicating control.
Two Forms with Many Strains
Avian influenza (AI) viruses exist throughout the world in many different strains.
Avian flu is an Influenza A virus that infects birds, and certain strains have been known
to infect both animals and humans. Avian flu is characterized by two forms in birds:
! a low pathogenicity (LPAI) form that causes mild illness, and
! a highly pathogenic (HPAI) form that is extremely contagious, causes
severe illness, and frequently has high rates of mortality.3
Both forms are possible in several strains. Strains are identified by two surface
proteins designated by the letters H and N.4 Some low pathogenic strains (H5 and H7)
are capable of mutating into highly pathogenic strains, and are thus treated nearly as
aggressively. For example, during a 1999-2001 epidemic in Italy, an LPAI virus (H7N1)
mutated into HPAI within nine months.
Because LPAI is endemic in wild bird populations, low pathogenicity outbreaks are
not uncommon. The 2004 outbreaks in the United States included low pathogenicity
2 International organizations include the U.N. Food and Agriculture Organization (FAO)
[http://www.fao.org/ag/againfo/subjects/en/health/diseases-cards/special_avian.html], the World
Health Organization (WHO) [http://www.who.int/csr/disease/avian_influenza/en], and the World
Organization for Animal Health (OIE) [http://www.oie.int/eng/avian_influenza].
3 Tests for pathogenicity are conducted in two ways. The first is through genetic (DNA)
sequencing. The other is by inoculating healthy chickens and monitoring their immune response
and mortality over a 10-day period. HPAI strains can result in greater or lesser rates of mortality,
perhaps ranging from 30-100%. LPAI strains typically do not exceed 10-20 percent mortality.
4 The surface proteins are called hemagglutinin and neuraminidase, abbreviated H and N. Fifteen
H subtypes and nine N subtypes have been identified, and they can occur in any combination.

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strains of H7N2 in Delaware, Maryland, and New Jersey, and H2N2 in Pennsylvania.
A strain classified as highly pathogenic H5N2 was found in Texas, although it did not
manifest as highly pathogenic. Other recent outbreaks in U.S. poultry include low
pathogenicity H7N2 in Connecticut and Rhode Island in 2003, and in Virginia, West
Virginia, and North Carolina in 2002. There have been only three highly pathogenic
outbreaks in the United States (1924, 1983, and 2004).
Transmission
Wild birds are the primary natural reservoir for Influenza A viruses and are often the
vector that introduces new outbreaks into domestic flocks. Wild birds often are resistant
to the virus and do not show clinical symptoms. The role of migratory birds is of
increasing concern, although, in the past, scientists have not been sure that infected birds
were able to migrate long distances.
Avian flu can be highly contagious in domestic poultry. The virus is spread by
contact with infected feces, nasal, or eye excretions. Once present in domestic flocks,
human activity becomes a risk for further transmission as people, clothing, vehicles, and
supplies move between farms. Thus, strict biosecurity measures are practiced among
commercial poultry farms and are encouraged by USDA and international agricultural
organizations such as the FAO.5
In the United States, avian flu viruses have been common in live bird markets
concentrated in urban areas with ethnic communities. Biosecurity practices can often be
lacking or insufficient if birds and equipment intermingle in the market or move back to
farms. Thus sanitation of crates, periodic disinfection of the market, and restrictions on
moving birds back into general farm populations are needed. USDA has focused on these
markets as one of the first places to control the disease. Live bird markets are a small
portion of the U.S. poultry industry (about 1/4 of 1%), but the frequency of outbreaks is
of concern to the majority of commercial growers practicing tighter biosecurity protocols.
In Asia, a larger network of live bird markets and the much larger number of small
backyard farms have posed significant problems for eradicating the disease.
Human infection. Avian flu can infect humans through poultry-to-human
transmission, usually through contact with fecal matter or other live bird excretions. The
World Health Organization (WHO) and the World Organization for Animal Health (OIE)
conclude that avian flu is not a food-borne disease since the virus is killed by the
temperature reached in normal cooking. The Centers for Disease Control and Prevention
(CDC) recommends standard food safety practices.
The human disease caused by H5N1 differs from typical human flu. H5N1 can
replicate in a wide range of cells, more so than the usual flu virus. This can result in a
severe disseminated disease affecting multiple organs, which has caused high rates of
mortality. The human vaccine currently available for mass inoculation in the fall of 2005
is felt to offer little protection against H5N1; vaccine trials and development are
underway. Public health professionals are concerned that the virus could mutate or
5 For biosecurity recommendations, see the USDA “Biosecurity for the Birds” website at
[http://www.aphis.usda.gov/vs/birdbiosecurity/hpai.html].

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combine with human flu viruses. If such a mutation were to occur, allowing efficient
human-to-human transmission, a more serious public health problem would result.
The number of human cases of H5N1 confirmed by WHO during the current
outbreak (December 2003-November 9, 2005) totals 125, resulting in 64 deaths (a 51%
mortality rate). Four countries have had human cases: Vietnam (92 cases, 42 deaths),
Thailand (20 cases, 13 deaths), Indonesia (9 cases, 5 deaths), and Cambodia (4 cases and
4 deaths). Some scientists believe that if the virus evolves to allow human-to-human
transmission, the mortality rate may decline, but whether this happens remains unknown.
The first human cases of H5N1 were in Hong Kong in 1997 (18 cases, 6 deaths).
Two other strains are documented to cause human illness: H7N7 in the Netherlands in
2003 (83 cases, 1 death), and H9N2 in Hong Kong in 1999 and 2003 (3 cases).
In the United States, the 2002 low pathogenic outbreak in poultry in Virginia resulted
in limited evidence of one human case. A man involved in the poultry depopulation effort
was found to have antibodies for H7N2 avian flu. In the fall of 2003, a man from
Westchester County, New York, contracted and recovered from H7N2 avian flu. The case
was not initially diagnosed as avian flu, and CDC first confirmed diagnosis in April 2004.
Control
Controlling avian flu in poultry through prevention and eradication is done
domestically by individual farmers in cooperation with state and federal governments, and
with industry associations and international organizations. In the United States, the
USDA Animal and Plant Health Inspection Service (APHIS) is the lead federal agency.
Internationally, the U.N. Food and Agriculture Organization (FAO) has a joint
response plan with WHO for the current outbreak. The $140 million, three-year plan is
being implemented but is not fully funded by donor countries. The United States has
contributed about $25 million.6
Preventing Infection. Biosecurity practices are the most important means of
preventing outbreaks in poultry. This includes preventing access of wild birds to
domestic flocks and limiting access to farm buildings by outside conveyances. For
example, delivery trucks and personnel are cleaned and disinfected before entering a
farm’s biosecure area. In Asia and other parts of the world, the large number of small
farms or backyard flocks without biosecurity practices has posed greater problems for
control. Such animal husbandry practices are slow to change.
Eradicating Outbreaks. Because the virus is highly contagious and easily spread
in poultry, the most common method of control after there is an outbreak is culling (also
called “stamping out,” depopulating) the infected flocks, and certain flocks in close
proximity to the infected flock. Federal statute allows such destruction of animals (9 CFR
6 “A Global Strategy for the Progressive Control of Highly Pathogenic Avian Influenza (HPAI),”
U.N. Food and Agriculture Organization (FAO) and World Organization for Animal Health
(OIE), in cooperation with the World Health Organization (WHO), November 2005
[http://www.fao.org/ag/againfo/subjects/documents/ai/HPAIGlobalStrategy31Oct05.pdf].

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53.4). Quarantines of surrounding areas are imposed (usually by state authorities) until
the disease is eradicated. Following depopulation, buildings and equipment are rigorously
disinfected before new birds are allowed, a process that takes at least several weeks. The
virus is killed by common disinfectants or heat (about 160 degrees F).
Vaccines. While vaccination of poultry is possible and has been used on a small
scale with some success, it generally is not considered a viable or sufficient control
method. Vaccination poses problems for international trade as many countries will not
import poultry products from other countries that use vaccination as a means of control,
since animals will test positive for antibodies. If vaccination is not administered and
monitored correctly, it can also allow the virus to become endemic and continue to spread
or mutate.7
In November 2005, USDA has a stockpile of 40 million doses of vaccine (for two
types of H5 and two types of H7 viruses). The Administration’s recent funding request
for avian flu (discussed below) includes a proposal to double USDA’s stockpile.
Federal Response to Domestic Outbreaks. Domestic outbreaks usually are
managed through joint federal, state, and industry cooperation. States usually lead the
response in terms of depopulation and quarantines. APHIS provides personnel and
equipment to advise and supplement state resources. In highly pathogenic outbreaks,
APHIS may take a larger role. The USDA National Veterinary Services Lab (NVSL) in
Ames, IA, conducts confirmatory tests on the pathogenicity and type of virus. USDA also
works to limit export restrictions to small geographic areas (such as states or counties)
and reopen export markets once outbreaks are eradicated.
Indemnities to Farmers. Compensation programs are desired to encourage
farmers to report outbreaks and cooperate with disease control programs. Indemnification
programs for low pathogenicity outbreaks generally are managed by the states. Some
industry associations, such as those on the Delmarva peninsula (Delaware, Maryland, and
Virginia), have compensation funds. In the past, USDA has not had a standing
compensation program for low pathogenicity avian influenza.8 However, a new program
is being developed following increased appropriations for a low pathogenicity program
in FY2005. When indemnification is offered by USDA, the standard rate for low
pathogenicity programs is 50% of fair market value. For highly pathogenic outbreaks of
avian flu, statute allows USDA to offer 100% indemnification (9 CFR 53.2).
7 See two journal articles by scientists at the World Organization for Animal Health (OIE): Ilaria
Capua and Stephano Marangon, “Vaccination for avian influenza in Asia,” Vaccine, 22 (2004),
4137-7138 [http://www.oie.int/eng/avian_influenza/vaccination%20in%20Asia.pdf], and Ilaria
Capua & Stephano Marangon, “The use of vaccination as an option for the control of avian
influenza,” Technical Item of the 71st General Session of the OIE, May 2003,
[http://www.oie.int/eng/avian_influenza/A_71%20SG_12_CS3E.pdf].
8 A limited USDA indemnification program was created for an LPAI outbreak in Virginia in 2002
(9 CFR 53.11). The Administration’s FY2005 budget request includes a proposal for an LPAI
indemnification program.

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Economic Impacts
The economic effects of any avian influenza outbreak can be significant. Expenses
to conduct depopulation and quarantines, as well as the direct loss of production, affect
local farms and regions. However, bigger economic effects come from international trade
bans. Localized quarantines and bans on the sale or movement of birds can affect farmers
outside the immediate quarantine area.
The United States is the world’s largest producer and exporter of poultry meat and
the second-largest egg producer. USDA estimates that about 8.5 billion broilers were
produced in 2003, and total poultry production was worth $23.3 billion (out of $105
billion for all livestock, and $200 billion total of crops and livestock). Broiler production
was valued at $15.2 billion, followed by eggs at $5.3 billion, and turkeys at $2.7 billion.
The U.S. exports about 16% of its poultry production.9
No estimates of the potential effect from an H5N1 outbreak in the United States are
available because of the highly uncertain nature of any possible, hypothetical outbreak.
The 1983-84 outbreak of highly pathogenic avian flu in the United States caused the
destruction of 17 million birds and cost $65 million. In the small 2004 domestic
outbreak, about 400,000 chickens were depopulated in the United States. This was less
than 1/200 of 1% of the 8.5 billion broilers slaughtered in the U.S. for food annually.
Yet, the effect on local regions and individual farms can was much greater.
Federal Appropriations to Control Avian Flu in Poultry
Federal appropriations for avian influenza have grown significantly in recent years.
In FY2004, Congress provided APHIS with $994,000 for avian flu for monitoring and
control. Following the 2004 domestic outbreak, USDA used emergency authority to
release $13.7 million of Commodity Credit Corporation (CCC) funds to accelerate its
avian flu plans. In FY2005, Congress appropriated APHIS $23.8 million for avian flu,
with about half for indemnities. For FY2006, the APHIS appropriation for avian flu is
$13.8 million. The conference agreement for agriculture appropriations (H.R. 2744,
H.Rept. 109-255) notes that $28.3 million is available, including carryover, with about
$12 million for indemnities.
The Emergency Supplemental Appropriations Act of 2005 (P.L. 109-13) provided
$25 million to the U.S. Agency for International Development (USAID) and CDC to
combat the spread of avian flu. Conferees encourage U.S. cooperation to support FAO
and WHO on a joint international plan (the FAO/WHO plan mentioned above).
On November 1, 2005, President Bush submitted a request to Congress for $7.1
billion in emergency funding to address avian flu in both humans and poultry. Of this
amount, $91 million would go to USDA ($73 million to APHIS for domestic activities,
$7 million to the Agricultural Research Service, and $11 million for international
activities in the form of technical assistance on surveillance, biosecurity, culling,
vaccination, and control).
9 The top five states in broiler production are Georgia (15%), Arkansas (14%), Alabama (13%),
Mississippi (9%), and North Carolina (9%), totaling 60% of U.S. broiler production.

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