A city worker sells eggs as people line up outside the truck in Mexico City on Aug. 24. The Mexican government is battling an egg shortage that has caused prices to spike in a country with the highest per-capita egg consumption on Earth. Alexandre Meneghini/AP hide caption

itoggle caption Alexandre Meneghini/AP

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

Chickens were killed in Hong Kong last December in an effort to halt the spread of the deadly H5N1 strain of bird flu. Aaron Tam/AFP/Getty Images hide caption

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Health Department officials cull birds and put them in sacks after bird flu virus was detected in Bhubaneswar, India. Biswaranjan Rout/AP hide caption

itoggle caption Biswaranjan Rout/AP

H5N1 avian flu viruses (seen in gold) grow inside canine kidney cells (seen in green). Cynthia Goldsmith/CDC hide caption

itoggle caption Cynthia Goldsmith/CDC

Virologists and other scientists are meeting at the World Health Organization's Geneva headquarters to talk about the bird flu. Pierre Virot/WHO hide caption

itoggle caption Pierre Virot/WHO

H5N1 avian flu viruses (seen in gold) grow inside canine kidney cells (seen in green). Cynthia Goldsmith/CDC hide caption

itoggle caption Cynthia Goldsmith/CDC