When a case of the potentially lethal H5N1 bird flu was found in British poultry in 2007, Dutch farmers were told to keep their poultry away from wild birds by closing off outdoor areas with wire mesh. Ed Oudenaarden/AFP/Getty Images hide caption

itoggle caption Ed Oudenaarden/AFP/Getty Images

National Institute of Allergy and Infectious Diseases Director Dr. Anthony Fauci said a voluntary halt to bird flu research should stay in effect. Chip Somodevilla/Getty Images hide caption

itoggle caption Chip Somodevilla/Getty Images

A government official in Bali, Indonesia, holds a chicken before administering an injection to cull it as a precautionary measure in April to prevent the spread of bird flu. Firdia Lisnawati/AP hide caption

itoggle caption Firdia Lisnawati/AP

Chickens are under quarantine in Tepatitlan, Jalisco State, Mexico. The Mexican government declared a national animal health emergency July 2 in the face of an aggressive bird flu epidemic that has infected nearly 1.7 million poultry. Hector Guerrero/AFP/Getty Images hide caption

itoggle caption Hector Guerrero/AFP/Getty Images

Vietnam has contained the fatal bird flu cases that raged in the late 2000s, but it is still struggling with new cases of the virulent disease. Here, a poultry trader loads live chickens onto his motorbike on March 16 at a market outside Hanoi. Hoang Dinh Ham/AFP/Getty Images hide caption

itoggle caption Hoang Dinh Ham/AFP/Getty Images

Balinese government officials prepare to cull chickens as a precautionary measure to prevent the spread of bird flu at a market in Denpasar on April 26. Firdia Lisnawati/AP hide caption

itoggle caption Firdia Lisnawati/AP

Local officials burn chicken coops in anticipation of a resurgence in bird flu in Jakarta, Indonesia, in January. Concerns about potential misuse of research into genes that control the contagiousness of flu have stymied publication. Tatan Syuflana/AP hide caption

itoggle caption Tatan Syuflana/AP