Order Code RS21747
Updated November 21, 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 mainly covers flu in poultry, and will be updated. For more on human
issues, see CRS Report RL33145, Pandemic Influenza: Domestic Preparedness Efforts,
by Sarah A. Lister.
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. The most recent
cases in domestic poultry, with three unrelated and less pathogenic strains, were in 2004.
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, several Asian countries have
had confirmed outbreaks of H5N1 in poultry, including Vietnam, Thailand, Indonesia,
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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Cambodia, China and Hong Kong, South Korea, Malaysia, Laos, and Japan. Since the
summer of 2005, H5N1 spread westward and has been confirmed in at least five new
countries: Russia, Kazakhstan, Turkey, Romania, and Croatia. Wild birds are one of the
main carriers, but their role 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.
The situation in Asia is historically unprecedented and extremely challenging. The
U.N. 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.2
International Control Efforts. As H5N1 spreads, it may become endemic in
countries with low levels of veterinary services or animal husbandry practices that harbor
the virus. Chances increase that the virus will evolve through mutation or reassortment
into a strain that could be transmitted easily between humans. Thus, FAO and the World
Health Organization (WHO) developed a strategy calling for the swift and coordinated
control of avian flu in poultry as the best way to prevent or delay a human pandemic from
developing, by reducing the number of animal hosts in which the virus may evolve.3
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:4
! 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.
Both forms are possible in several strains. Strains are identified by two surface
proteins designated by the letters H and N.5 Some low pathogenicity strains (H5 and H7)
2 For international issues, see the World Health Organization (WHO)
[http://www.who.int/csr/disease/avian_influenza/en], U.N. Food and Agriculture Organization
(FAO) [http://www.fao.org/ag/againfo/subjects/en/health/diseases-cards/special_avian.html], and
the World Organization for Animal Health (OIE) [http://www.oie.int/eng/avian_influenza].
3 “A Global Strategy for the Progressive Control of Highly Pathogenic Avian Influenza (HPAI),”
F A O a n d O I E , i n c o o p e r a t i o n w i t h W H O , N o v e m b e r 2 0 0 5
[http://www.fao.org/ag/againfo/subjects/documents/ai/HPAIGlobalStrategy31Oct05.pdf].
4 Tests for pathogenicity are conducted in two ways: through genetic (DNA) sequencing, and 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.
5 The surface proteins are called hemagglutinin and neuraminidase, abbreviated H and N. Sixteen
H subtypes and nine N subtypes have been identified, and they can occur in any combination.

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are capable of mutating into highly pathogenic strains, and thus are treated aggressively.
For example, in Italy in 1999, an H7 LPAI virus mutated into HPAI within nine months.
Because LPAI is endemic in wild birds, low pathogenicity outbreaks are not unusual.
The 2004 domestic outbreaks included low pathogenicity 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.
Only three highly pathogenic domestic outbreaks have occurred (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 organizations.6
In the United States, avian flu viruses have been common in live bird markets
concentrated in ethnic or urban areas. 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 0.25%), 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. Certain strains of 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
6 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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mortality. The human vaccine currently available for mass inoculation in the fall of 2005
does not protect against H5N1; vaccine trials and development are underway. Public
health professionals are concerned that the virus could mutate or combine with human flu
viruses to allow efficient human-to-human transmission.
The number of human cases of H5N1 confirmed by WHO during the current
outbreak (December 2003-November 17, 2005) totals 130, resulting in 67 deaths (a 51%
mortality rate). Five countries have had human cases. Vietnam (92 cases, 42 deaths) and
Thailand (21 cases, 13 deaths) have the most, with Indonesia, Cambodia, and China
having fewer. 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.
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. The USDA Animal and Plant Health Inspection Service
(APHIS) is the lead federal agency.
Internationally, FAO has a joint response plan with WHO for the current outbreak
(see footnote 3). The $140 million, three-year plan is being implemented but is not fully
funded by donor countries. The United States has pledged about $25 million.
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
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).

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Vaccines. While vaccination of poultry is possible and has been used on a small
scale with some success, it generally is not considered a sufficient control method.
Vaccination poses problems for international trade as many countries will not import
poultry products from other countries that use vaccination, since animals will test positive
for antibodies. If vaccination is not administered and monitored correctly, it can 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)
conducts confirmatory tests on the pathogenicity and type of virus. USDA also works to
limit export restrictions (such as to states or counties) and reopen export markets.
Indemnities to Farmers. Compensation programs are desired to encourage
farmers to report outbreaks and cooperate with control programs when culling is needed.
States generally manage indemnification programs for low pathogenicity outbreaks. 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 compensation
program for LPAI.8 However, a new federal program is being developed following
increased appropriations in FY2005 for a low pathogenicity program. USDA’s standard
indemnification for low pathogenicity programs is 50% of fair market value. For highly
pathogenic outbreaks, statute allows USDA to offer 100% indemnification (9 CFR 53.2).
Federal Appropriations to Control Avian Flu in Poultry
Federal appropriations for avian flu have grown significantly. In FY2004, Congress
provided APHIS with $994,000 for avian flu for monitoring and control. During the 2004
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 an indemnity reserve.
For FY2006, the new 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.
For international aid, the Emergency Supplemental Appropriations Act of 2005 (P.L.
109-13) provided $25 million to the U.S. Agency for International Development (USAID)
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,” May 2003, [http://www.oie.int/eng/avian_influenza/A_71%20SG_12_CS3E.pdf].
8 A limited indemnification program was created for an LPAI outbreak in 2002 (9 CFR 53.11).

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and CDC to combat the spread of avian flu. Conferees encourage cooperation with FAO
and WHO on a joint international plan (the FAO/WHO plan mentioned in footnote 3).
On November 1, 2005, President Bush submitted a request for $7.1 billion in
emergency funding to address avian flu in both humans and poultry. Of this amount, $91
million (1.3%) would go to USDA. This includes $73 million for APHIS for domestic
activities, $7 million for the Agricultural Research Service, and $11 million for
international activities (in the form of technical assistance on surveillance, biosecurity,
culling, vaccination, and control).
Congressional Hearings. The House and Senate agriculture committees held
hearings on avian influenza on November 16 and 17, 2005, respectively. Witnesses from
the Administration, academia, and industry reviewed efforts to prevent and control avian
flu outbreaks.9
Economic Impacts
The economic effects of any avian influenza outbreak can be significant. Direct
costs include expenses to cull birds and quarantine farms, and lost production on affected
farms. However, larger economic effects arise from international trade bans which can
cause price changes that affect farms outside the quarantine area. If consumer confidence
remains high, demand for healthy poultry may rise; but if consumer confidence lags,
poultry prices may drop. Markets for substitute meats may also be affected, as can
markets for feed such as corn (both domestic and exported).
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 farm sales of poultry were worth $23.3 billion (out of $105 billion
for all livestock, and $200 billion including crops). Broiler production was $15.2 billion,
followed by eggs at $5.3 billion, and turkeys at $2.7 billion. Five states account for 60%
of U.S. production: Georgia (15%), Arkansas (14%), Alabama (13%), Mississippi (9%),
and North Carolina (9%). The U.S. exports about 16% of its poultry production.
No economic estimates of an H5N1 outbreak in the United States are provided
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. While this was less than 0.02%
of U.S. broiler production, the effect on local regions and farms was much greater.
9 The statement of the APHIS Administrator, the witness at the House hearing, is available at
[http://agriculture.house.gov/hearings/109/h51116w1.pdf]. Statements from Senate witnesses
are available at [http://agriculture.senate.gov/Hearings/hearings.cfm?hearingId=1691].

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