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