Food safety in the United States is regulated mainly by the U.S. Department of Agriculture (USDA) and the Food and Drug Administration (FDA) within the U.S. Department of Health and Human Services (HHS). Although the FDA is the federal agency primarily responsible for ensuring the safety of a vast majority of foods under the current system, the USDA is responsible for regulating meat, poultry, and some egg products, as well as being responsible for animal and plant health. USDA's role in the food safety system is founded on its authority to regulate meat and poultry inspection and importation. The Food Safety and Inspection Service (FSIS) within USDA is responsible for inspecting domestic and imported meat and poultry products under the Federal Meat Inspection Act and the Poultry Products Inspection Act. This role in inspection of meat and poultry generally begins beyond the farm at slaughter and processing facilities. This authority does not include direct regulation of on-farm practices related to animal health. However, as the next step in the food chain after the farm, the standards set for inspection may be seen to indirectly regulate the health of animals on the farm. The Egg Products Inspection Act may be interpreted similarly. In other words, these acts restrict acceptance of animals that do not meet health standards at slaughtering and processing facilities, which effectively require farms to maintain healthy livestock in order to sell their livestock for food processing. Food safety regulation is not limited to processing plants. USDA has authority to exercise food safety oversight and enforcement on farms as well. Four statutes that provide the most significant authority related to on-farm activity and food safety are the Animal Health Protection Act, the Plant Protection Act, the Agricultural Marketing Agreement Act of 1937, and the Agricultural Marketing Act of 1946. The Animal and Plant Health Inspection Service (APHIS) within the USDA is responsible for the protection of health of animals and plants from agricultural pests and diseases. Issues of animal and plant health are of interest not only in the food safety context, but also in trade matters and the agricultural industry generally. Outbreaks of disease among animals may lead to negative consequences for the U.S. agricultural system and also may have negative effects on international trade if U.S. agricultural resources are deemed unsafe for import and consumption in other countries. The USDA's on-farm authority includes authority to monitor animal health, which would assist in government efforts to prevent the spread of some diseases from animals to human populations ( e.g. , bovine spongiform encephalopathy, or "mad cow disease"). Although there has been some concern about an April 2009 outbreak of influenza A(H1N1), initially dubbed "swine flu" because it contained genetic material from flu strains that normally circulate in swine, USDA has confirmed that "there is no evidence of the 2009-H1N1 virus in U.S. swine." The virus, however, is not a foodborne illness, meaning that it is not transmitted by consumption of certain foods like pork and pork products. Under authority currently in place, USDA may monitor or take other protective actions to prevent outbreaks of such diseases, whether they pose a foodborne or airborne risk to the health of other animals or humans. Congress enacted the Animal Health Protection Act (AHPA) as part of the 2002 farm bill in order to protect animal health through the prevention and control of animal diseases and pests. AHPA generally authorizes USDA to prohibit or restrict the importation, exportation, or entry of animals into interstate commerce if it determines such action is necessary to prevent the introduction or dissemination of any pest or disease of livestock. The AHPA also generally authorizes USDA to hold, seize, quarantine, or destroy any animal that is in interstate commerce and is believed to be carrying or have been exposed to any pest or disease of livestock. Most of USDA's authority under AHPA relates to animals moving in interstate commerce, but the AHPA specifically permits USDA to take some actions without explicitly requiring that the animal be in interstate commerce at the time. USDA is authorized to take protective actions such as seizing, treating, or destroying animals if the USDA determines that "an extraordinary emergency exists because of the presence in the United States of a pest or disease of livestock." For such emergencies, the presence of the pest or disease must threaten U.S. livestock and the protective action must be necessary to prevent the spread of the threat. USDA is also authorized to make inspections and seizures under the AHPA at any premises, including farms, if it obtains a warrant showing probable cause to believe there is an "animal, article, facility, or means of conveyance regulated under [the AHPA]." This inspection authority supplements USDA's authority to make warrantless inspections of any person or means of conveyance moving in interstate commerce that is believed to be carrying an animal regulated by AHPA. The AHPA also provides broad authority to USDA for detection, control, and prevention of the introduction and spread of outbreaks of animal diseases and pests. AHPA authorizes USDA to "carry out operations and measures to detect, control, or eradicate any pest or disease of livestock (including ... diagnostic testing of animals), including animals at a slaughterhouse, a stockyard, or other point of concentration." AHPA also expanded APHIS's authority to protect against the introduction of plant and animal disease and "otherwise improve the capacity of the [APHIS] to protect against the threat of bioterrorism." APHIS used this authority to implement a voluntary system of animal tracking known as the National Animal Identification System, which allows for registration of premises where livestock and poultry are raised or housed, identification of animals with unique identifier information, and tracking of identified animals. The Plant Protection Act (PPA), enacted in 2000, provides protections similar to the AHPA but specifically applies to plants, rather than animals. The PPA was enacted to control and prevent the spread of plant pests for the protection of the agriculture, environment, and economy of the United States by regulating plant pests and noxious weeds that are in or affect interstate commerce. The PPA defines plant pests as certain organisms "that can directly or indirectly injure, cause damage to, or cause disease in any plant or plant product." It defines noxious weeds as "any plant or plant product that can directly or indirectly injure or cause damage to crops ... , livestock, poultry, or other interests of agriculture, irrigation, navigation, the natural resources of the United States, the public health, or the environment." Under the PPA, the USDA has authority to prohibit or restrict the movement of plants and plant products in interstate commerce if it determines such action would be necessary to prevent the introduction or spread of plant pests or noxious weeds. APHIS has used the PPA to monitor genetically engineered crops that may cause negative effects on other agricultural products. The PPA authorizes USDA generally to hold, quarantine, treat, or destroy any plant, plant pest, or noxious weed that is moving or has moved in interstate commerce if it deems such action necessary "to prevent the dissemination of a plant pest or noxious weed that is new to or not known to be widely prevalent or distributed" in the United States. USDA may also order owners of plants, plant products, plant pests, or noxious weeds that are determined to threaten plant health to treat or destroy them. USDA's ability to impose remedial measures under this authority is limited, though. That is, USDA may not require that a plant, plant product, plant pest, or noxious weed be destroyed or exported if the Secretary believes there is a less drastic, feasible and adequate alternative available to prevent dissemination of the threat. In addition to the general authority to prevent the spread of plant pests and noxious weeds, USDA also has emergency authority under PPA. For USDA to act under its emergency authority, it must find "that the measures being taken by the State are inadequate to eradicate the plant pest or noxious weed" after consulting with the governor of the affected state. Under the PPA, if USDA determines that "an extraordinary emergency" exists, it may hold, seize, quarantine, treat, or destroy any plant, plant product, or premises that it "has reason to believe is infested with the plant pest or noxious weed." Like the limitation under its general authority to impose remedial measures, the USDA is prohibited from destroying or exporting anything under its emergency authority if there is a less drastic, feasible action "that would be adequate to prevent the dissemination of any plant pest or noxious weed new to or not known to be widely prevalent or distributed [in] the United States." Although the AHPA and PPA may provide more significant sources of authority for USDA to take regulatory actions on farms, other statutes provide USDA with oversight authority related to farm activities and food safety. The Agricultural Marketing Service (AMS) within the USDA oversees programs related to the standardization and marketing of agricultural products. The Agricultural Marketing Agreement Act of 1937 and the Agricultural Marketing Act of 1946 authorize programs that may involve oversight of producers regarding food quality and safety. The Agricultural Marketing Agreement Act of 1937 (AMAA) authorizes USDA to issue marketing orders that legally bind processors, associations of producers, and others engaged in the handling of certain agricultural commodities or products thereof. The AMAA provides a list of terms and conditions that may be included in marketing orders. Orders must include at least one of the possible terms and conditions provided by statute, and may not include other terms and conditions not provided by statute. The possible terms and conditions include regulating the amount, grade, size, or quality of the marketed commodity; regulating the containers used for packaging, transportation, sale, and handling of the marketed commodity; and requiring inspection of any commodity or product. Thus, depending on what terms and conditions are included in a marketing order, the order may create legally binding requirements relating to food quality and safety.