Swine flu refers to strains of influenza ("flu") that occur naturally and may cause outbreaks of respiratory illness among wild and domestic pigs. People do not normally get swine flu, but each year the Centers for Disease Control and Prevention (CDC) identifies a few isolated cases of human flu that are caused by flu strains typically associated with swine. The current outbreak of concern is caused by a new strain of flu virus that produces illness in people. It is one of several flu virus strains designated as influenza A(H1N1) for specific proteins on their surface. This new virus was first detected in people in the United States in April 2009. Mexico, Canada, and other countries around the world have reported human cases of illness from the new flu strain. The virus appears to spread from person to person in much the same way as with seasonal flu. This virus was originally referred to as "swine flu" because laboratory testing showed that many of its genes were similar to flu viruses that normally occur in pigs in North America. Further study has shown that this new virus is very different from what normally circulates in North American pigs. It has two genes from flu viruses that normally circulate in pigs in Europe and Asia, as well as genes from flu strains that normally circulate in humans and in birds. At this time, there is no evidence that pigs were involved in the transmission of the new flu virus to humans. For more background information, see CRS Report R40554, The 2009 Influenza Pandemic: An Overview . General information is also available at the CDC and WHO websites. The CDC, the WHO, and the World Organization for Animal Health (OIE) confirm that there is no evidence that 2009 H1N1 virus is transmitted by food. These organizations have repeatedly emphasized that humans cannot get 2009 H1N1 flu, or any other type of flu, from eating pork or pork products. Some have further emphasized the importance of eating properly handled and cooked pork and pork products, and recommend cooking pork to an internal temperature of 160°F/70°C. This corresponds to the general guidance for the preparation of pork and other meat to kill all viruses and other foodborne pathogens. The U.S. Department of Agriculture (USDA) has repeatedly said that the 2009 H1N1 flu is not a foodborne disease and that eating properly handled and cooked pork or pork products is safe. These same arguments were made by medical and veterinary authorities at congressional hearings. The American Veterinary Medical Association (AVMA) further claims that "neither exposure to pigs nor consumption of pork are risk factors for infection." Four intergovernmental organizations—WHO, OIE, the World Trade Organization (WTO), and the United Nations Food and Agriculture Organization (FAO)—issued a joint statement that "pork products handled in accordance with hygienic practices are not a source of infection." The European Centre for Disease Prevention and Control (ECDC) also states that "influenza virus is not transmitted by eating properly handled and cooked pork and pork products," and the European Food Safety Authority (EFSA) claims it is "not aware of any scientific evidence of risk to pork consumers from influenza viruses regardless of the type of pork consumed." Given the safety of eating pork and pork products, along with the fact that the disease is primarily transmitted from human to human, several U.S. and international organizations argued that the disease should not be called "swine flu." The CDC, WHO, and OIE, among others, recommend instead referring to the disease by its scientific name, influenza A(H1N1) or 2009 H1N1. The WHO and CDC continue to emphasize that humans typically contact this type of flu through human-to-human contact, or through contact with infected pigs or environments contaminated with the virus. OIE has noted that pork and pork products, "handled in accordance with good hygienic practices recommended by the WHO, the Codex Alimentarius Commission, and the OIE, will not be a source of infection"; and it recommends that "authorities and consumers should ensure that meat from sick pigs or pigs found dead are not processed or used for human consumption under any circumstances." EFSA has further stated that it is "not aware of any scientific evidence of risk to pork consumers from influenza viruses regardless of the type of pork consumed," including raw meat, although it is quick to cite longstanding food safety advice that proper cooking kills bacteria or viruses which may be found in foods, and may prevent possible risk of foodborne illness. USDA is also reminding consumers to practice good food hygiene and "safe food handling and preparation techniques for all meat and poultry." In December 2009, USDA announced the results of a study providing additional confirmation that meat, blood, and tissue from pigs exposed to the 2009 novel pandemic H1N1 virus did not contain the H1N1 virus; the virus was only found in the animal's respiratory tract. CDC has acknowledged that the H1N1 flu virus can spread from pigs to people and from people to pigs, raising concerns that livestock workers who may be exposed to infected animals may be at risk of contracting the virus. CDC reports that recent studies show that 15%-25% of swine farmers may have been exposed to swine flu viruses at some time in their lives, as well as about 10% of veterinarians. CDC has published guidance for workers who are employed at commercial swine farms; the National Pork Board has also published biosecurity recommendations for producers. In May 2009, Canadian officials confirmed that the H1N1 flu virus was found in a swine herd in Alberta, Canada. This incident was reported to the OIE and was confirmed to have resulted from human-to-pig transmission. The Canadian Food Inspection Agency (CFIA) said it has taken all necessary precautions and has placed the herd under quarantine. CFIA maintains that Canadian pork continues to be safe to eat. In August, international food agencies announced that H1N1 had been detected in poultry farms, including turkey flocks in Chile. In October, USDA's National Veterinary Services Laboratories (NVSL) confirmed the presence of the H1N1 flu virus in a pig sample collected at the Minnesota State Fair submitted by the University of Minnesota. Later that month USDA announced the presence of the H1N1 virus in a commercial U.S. swine herd in Indiana. USDA and a network of federal veterinarians, state animal health officials, and private practitioners are regularly monitoring U.S. swine for signs of significant disease. In December, USDA further confirmed the first case of H1N1 flu virus in a U.S. turkey flock located in Virginia. Researchers have confirmed that the H1N1 flu virus likely originated in pigs and may have been circulating undetected in pigs for years. Some have speculated that the source of the outbreak might potentially be associated with operations with a large number of confined animals. Initial reports suggested that the 2009 H1N1 flu had possibly originated at a large confinement of Smithfield Foods Inc. located in Veracruz, Mexico. Smithfield has repeatedly reported that there is no evidence of the presence of 2009 H1N1 influenza in any of the company's swine herds or in its employees at any of its worldwide operations, including those in the United States. The U.S. Animal Health & Productivity Surveillance Inventory , maintained by USDA's Animal and Plant Health Inspection Service (APHIS), does surveillance for avian flu. Prior to the outbreak, USDA did not conduct surveillance for swine flu because of information limitations. Currently, the Inventory includes all animal health surveillance programs conducted by Veterinary Services, as well as all animal health monitoring studies completed by the National Animal Health Monitoring System (NAHMS). Information on certain additional animal health surveillance programs or studies conducted by USDA and other Federal agencies is also currently included. Following the outbreak, industry reports indicated that APHIS was working on draft guidelines and surveillance plans for the H1N1 virus. Other industry reports based on information prior to the outbreak also indicate that the CDC National Center for Immunization and Respiratory Diseases (NCIRD) Influenza Division (ID) and USDA APHIS Veterinary Services (VS, specifically the National Veterinary Services Laboratories or NVSL) entered into an interagency agreement regarding swine influenza virus (SIV) surveillance in July 2008. These same reports suggest that a parallel agreement was reached between CDC and USDA Agricultural Research Service (ARS) for related research efforts on isolates derived from the APHIS program. APHIS's Veterinary Services has since developed guidelines for managing potential cases of the virus in swine. These guidelines were developed in collaboration with the animal health, food safety, and public health communities. APHIS's National Animal Health Surveillance System (NAHSS), which monitors animal disease outbreaks—including swine influenza virus—in domestic animals, has released its surveillance plan for swine influenza virus. USDA has provided H1N1 virus to several animal vaccine makers, who are developing a vaccine. By December 2009, the first H1N1 swine vaccine was in use in the Midwest, but distribution was limited and heavily monitored. In late April, amid early reports of the spread of 2009 H1N1 flu, retail outlets reported that consumers were leery of buying pork because of fears that the disease might be linked to pork consumption. Tyson Foods Inc. also reported a drop in domestic pork sales. As domestic sales fell, retail and wholesale hog prices fell sharply, along with hog and pork-belly futures prices on the Chicago Mercantile Exchange. This drop in prices coincided with seasonal fluctuations in the hog market that would normally have caused prices to be higher. Economists at Purdue University estimated that Indiana hog producers were losing about $5 a head on April 24, compared to estimated losses of about $20 immediately following reports of the initial outbreak in March.