This report examines scenarios in which international trade could be heavily controlled or limited due to an avian flu pandemic. Each of the scenarios presented depicts the possibility that imports of goods into the United States could be curtailed due to the avian flu. Some experts argue that these scenarios are not likely to occur, because they believe that the United States would probably not implement a general ban on the importation of goods from affected regions. It is believed that such a ban would not prevent transmission of the avian flu to the United States, because there is little evidence that inanimate objects could transmit the disease. Furthermore, opponents to a general ban on imports argue that such actions could unnecessarily cause economic and social hardship. The United States depends on global trade for necessities such as food, energy, and medical supplies. Also, some observers point out that the nature of the "just-in-time" global economy is such that the United States does not stockpile these and other necessities. Finally, the World Health Organization does not recommend quarantining any individual country or closing international borders at any phase of an avian influenza pandemic. If international borders are not closed to human passage, then it follows that there will probably not be direct trade restrictions. While some experts believe that a general ban on imports either globally or from affected regions is highly unlikely, others contend that the strategy cannot be totally ruled out, particularly since there is already a U.S. ban on imports of poultry products from certain H5N1 (highly pathogenic strain of avian influenza)-affected countries and regions. Some experts argue that it may be possible to transmit the virus through any object that has had contact with infected feces, blood, or other bodily fluids. Some policy analysts predict that if the H5N1 virus were to become a pandemic with human-to-human transmission, then the United States might control the movement of people across its borders to slow the virus' arrival on U.S. soil. This could involve limiting airline passenger flights into the country, but it could also mean limiting entry of cargo ships due to a fear of transmission from ship operators or stowaway birds. These types of restrictions may result in a de facto import ban. Some experts believe these restrictions are unnecessary and potentially harmful, but they might nevertheless be implemented to give the appearance of strong preventative actions, in response to public concerns or political factors. Many believe that if such restrictive measures were adopted, they would likely be short-lived. Once the pandemic reached the United States, such measures would appear to serve little further purpose and could be abandoned. A more likely scenario is that a supply-side constraint in the exporting country would limit U.S. imports. Pandemic-affected countries could curtail their exports, either voluntarily or involuntarily. Governments may nationalize assets and stop export operations. An outbreak may also constrain production and key export infrastructure through excessive worker absences, to the point where exporting becomes difficult and is involuntarily slowed or halted. Such a slowdown in commerce could cause price increases or temporary shortages in certain goods within the United States, depending on the duration and breadth of the slowdown. It could exacerbate the effects of slowed production and distribution networks within the United States, leading to decreased demand and supply and a recession. Several studies have been undertaken to estimate the effects of a pandemic on the U.S. and global economy. According to one study, a mild pandemic could reduce global economic output by $330 billion, or 0.8% of global gross domestic product (GDP). The same study estimates that a pandemic of the worst case scenario severity could reduce global economic output by $4.4 trillion, or 12.6% of global GDP. The Congressional Budget Office (CBO) estimates that a severe influenza pandemic might cause a decline in U.S. GDP of about 4.25%, and that a milder pandemic might cause a decline of about 1%. Other studies have found both greater and lesser economic effects, depending on the methodology and data used. Different studies also disagree on the extent to which international trade would be disrupted by an avian flu pandemic. This section considers the potential economic and trade effects on the United States of import disruptions from countries affected by avian flu, either as a result of border closings in the United States or supply side constraints in the exporting country or region. Only countries with human avian flu cases confirmed by the World Health Organization (WHO) from January 2004 to January 2008 are considered, because these countries are arguably more likely to experience trade disruptions due to avian flu. The relative likelihood of import disruptions from one country or region over another is not considered, because it is too difficult to ascertain. As seen in Table 1 , the United States imports far more from China than any other country that has thus far reported confirmed human cases of the avian flu. In fact, China is the largest source of U.S. imports overall, accounting for over 16% of total U.S. imports in 2007. Therefore, if imports from China were disrupted on a large scale over a long time period, it could have a significant effect on the U.S. economy. However, a short-lived disruption in imports from China may not cause an immediate crisis. Forty-four percent of U.S. imports from China are in the category of machinery or electronic machinery, and include items such as computers, televisions, and parts. A disruption in imports of these items could have implications for the domestic electronics market, but it may have a less severe effect on the U.S. economy as a whole. One import category of special concern is medical supplies; the United States imported over $5 billion in optical and medical instruments from China in 2007, representing 10% of such U.S. imports. Many, but not all, products in this category are considered essential medical equipment. For example, China was the second-largest supplier (after Mexico) of respirator equipment to the United States, supplying over 13% of U.S. respirator equipment imports. China has also been an important supplier of bandages (41% of U.S. imports in 2007), boxed first aid kits (53%), clinical thermometers (50%), orthopedic appliances (9%), and syringes (13%). Some observers recommend that U.S. hospitals stockpile essential supplies to take a possible avian flu pandemic into account, especially considering that medical supplies are sourced from potential avian flu hot spots. Many of these essential medical supplies are reportedly not manufactured in the United States. Almost 15% (about $1.5 billion) of fish and seafood imports into the United States are from China, second only to Canada ($1.9 billion). It is not clear whether a trade disruption with China alone would have a great impact on the U.S. food supply, since the United States also imports food from other countries and regions, in addition to having domestic production. Although the United States imports a great deal from China, many of these products originate elsewhere, and only their final stage of production takes place in China. For some items, production could possibly be shifted to another location if a long-term trade disruption were to occur. However, shifting production in the global supply chain may have great costs or not be feasible for other reasons. Thailand, Indonesia, and Vietnam have similar patterns of exports to the United States, although in different volumes. Among countries with confirmed human avian flu cases, Thailand is the second largest supplier of U.S. imports. However, Thailand's total 2007 exports to the United States were just under $23 billion, and it ranked 18 th out of all exporters to the United States, with 1.2% of the U.S. import market. Indonesia and Vietnam were ranked 26 th and 31 st , respectively, with $14 billion and $11 billion in 2007 U.S. imports. Like China, Thailand's main exports to the United States are electrical machinery and machinery, comprising about 44% of Thailand's exports to the United States. Thailand, Indonesia, and Vietnam all export large quantities of fish to the United States. Thailand is the largest exporter of prepared crustaceans and mollusks (the second largest is China), and the second largest exporter of fresh crustaceans to the United States (after Canada). Indonesia and Vietnam are the third and fifth largest suppliers of prepared crustaceans, and the fourth and third largest suppliers of fresh crustaceans to the United States. Thailand and Indonesia also export optical and medical instruments to the United States, ranking 21 st and 28 th , respectively, in 2007 U.S. imports. The United States imports medical supplies such as dialysis instruments, diagnostic instruments, syringes, needles, and ultrasound devices from Thailand and Indonesia. In analyzing the trade data, it appears that if trade were disrupted between the United States and any one of Thailand, Indonesia, or Vietnam, the effects would probably be minimal. However, if U.S. trade was disrupted with all three countries and China (considered more likely under a flu pandemic), the U.S. supply of seafood and medical supplies could be impaired. Reduced seafood imports could increase not only the price of seafood, but it could cause increased demand and possible price increases in substitute goods. The impact of reduced medical supply imports could be more severe, possibly resulting in a shortage of certain medical supplies, since substitutes are generally not readily available. Oil comprised 95% ($10.8 billion) of U.S. imports from Iraq in 2007, representing 3% of U.S. oil imports. Iraq is the ninth-largest oil exporter to the United States. If oil imports from Iraq were to stop, the reduced supply of oil could cause domestic energy prices to increase. However, there are many factors determining domestic energy prices, and other events could overshadow, exacerbate, or offset any disruption of trade with Iraq due to an avian flu pandemic.