TIMELINE-Tracing the bird flu outbreak in N. American poultry flocks

June 12 (Reuters) - The United States is facing its worst outbreak on record of avian influenza in poultry as three deadly strains have hit North American flocks since December. More than 47 million chickens and turkeys have been killed or will be culled, and U.S. egg prices are projected to set an annual record high because of the losses.

So far, highly pathogenic avian influenza (HPAI) has been confirmed in 21 U.S. states, either in commercial flocks, wild birds, or both. Four states have declared an emergency: Iowa, Minnesota, Nebraska and Wisconsin. The virus has also been confirmed in the Canadian provinces of British Columbia and Ontario.

Below is a timeline of the spread of the disease, according to the U.S. Department of Agriculture’s Animal and Plant Health Inspection Service (APHIS), Canada’s Food Inspection Agency (CFIA), and responses by the industry and trade partners.

Wild birds are thought to be carriers of the virus, which also can be tracked onto poultry farms by people or trucks that come into contact with contaminated feces. It may also be carried into poultry barns by wind blowing in contaminated dirt or dust.

Dec. 2, 2014 - The CFIA quarantines two turkey and chicken farms in Canada’s British Columbia province after an H5 type of avian influenza is detected there, later confirmed to be the H5N2 strain.

Dec. 3 - South Korea, Hong Kong, Taiwan and Japan impose restrictions on British Columbian poultry and products.

Dec. 8 - The United States suspends imports of birds and hatching eggs, poultry meat, eggs and egg products and animal byproducts from British Columbia.

Dec. 19 - The outbreak’s first U.S. case is confirmed as H5N8 avian influenza strain is found in a mixed poultry flock in Douglas County, Oregon.

Dec. 20 - South Korea, one of the top buyers of U.S. poultry, halts imports of poultry and poultry products from the United States.

Jan. 3, 2015 - The first case of the highly contagious H5N2 avian influenza strain confirmed in a backyard flock of 140 mixed birds in Benton County, Washington.

Jan. 6 - Mexico, the largest market for U.S. poultry at $1.2 billion in 2014, bans imports from states with confirmed cases.

Jan. 7 - No. 2 U.S. poultry importer Canada bans imports from affected areas.

Jan. 8 - Imports of U.S. poultry, poultry products and eggs banned by China.

Jan. 23 - H5N8 appears for the first time in a commercial turkey flock of 134,400 birds in California.

Feb. 2 - The CFIA finds the H5N1 virus in a backyard poultry flock in British Columbia.

Feb. 12 - The first commercial chicken flock is hit with H5N8. The Kings County, California, flock had 112,900 birds.

March 4 - The first instance of highly pathogenic avian influenza (HPAI) along the Mississippi migratory flyway is confirmed in a commercial flock of 26,310 turkeys in Minnesota, the top U.S. turkey producing state. The flyway runs from the Gulf of Mexico to the northern Midwest along the Mississippi River valley. The virus is thought to be traveling with wild birds as they migrate north.

April 6 - The CFIA confirms an H5 HPAI strain on a turkey farm in Ontario. A day later, Japan and Taiwan impose restrictions on poultry and products from the region.

April 11 - The H5N2 strain is confirmed for the first time in a commercial chicken operation, hitting 200,000 egg-laying hens in Jefferson County, Wisconsin.

April 20 - The biggest flock hit so far, as H5N2 is confirmed in 4 million egg-laying hens in Osceola County, Iowa. Mexico expands its import ban to include live birds and eggs from Iowa - the top egg-producer in the United States.

April 20 - Wisconsin declares a state of emergency.

April 23 - Minnesota declares a state of emergency.

April 29 - Saudi Arabia, the world’s second-largest importer of chicken broiler meat, bans imports of poultry meat and egg products from Ontario.

April 29 - A chicken broiler breeding farm in Kossuth County, Iowa, initially tests positive for H5 bird flu, believed to be the first case at a broiler breeding farm.

May 1 - USDA confirms bird flu in nine more commercial flocks, including a 4.9 million-bird flock of egg-laying hens in Buena Vista County, Iowa, the largest finding to date.

May 1 - Iowa declares a state of emergency.

May 5 - U.S. government approves $330 million in emergency funds to fight bird flu spread.

May 11 - USDA confirms H5N8 avian flu in a backyard poultry flock in Indiana.

May 12 - USDA confirms H5N2 avian flu at a commercial egg-laying farm in Nebraska.

May 14 - Nebraska declares a state of emergency.

May 22 - Some U.S. food companies are scouting for egg supplies abroad, due to the flu outbreak. It is estimated that about 30 percent of U.S. breaker eggs - which includes liquid, dried or frozen eggs used by food manufacturers - has disappeared in the wake of the virus.

June 8 - Michigan says Canada geese in the state test positive for lethal strain of bird flu, becoming the sixth state to detect it only in wild or free-ranging birds.

June 11 - A U.S. Senate committee says it will hold a hearing in July on the outbreak, amid mounting criticism from Iowa lawmakers about the speed of the USDA’s response. (Reporting by Karl Plume, Tom Polansek and P.J. Huffstutter in Chicago; Editing by Bernard Orr and Matthew Lewis)