Bird flu found in Oklahoma dairy herd, showing bigger US outbreak

July 15 (Reuters) -

Oklahoma has become the 13th U.S. state to detect bird flu in dairy cows, the U.S. Department of Agriculture confirmed on Monday, though the state said the infection happened months ago.

The confirmation shows the outbreak was more widespread than U.S. authorities knew after the virus was first found in dairy cattle in late March. Bird flu has since been detected in more than 150 dairy herds nationwide.

The cases are part of a

far-reaching outbreak

of H5N1 bird flu that has been spreading globally in wild birds, infecting poultry and various species of mammals. Four dairy workers have tested positive this year. The U.S. Centers for Disease Control and Prevention has said the risk to the general public remains low.

An Oklahoma dairy collected the positive sample in April when it suspected its herd may have been infected, said Lee Benson, spokesperson for the Oklahoma Department of Agriculture, Food and Foresty. The dairy recently sent stored samples to USDA for testing after the farm learned it could receive financial assistance for lost milk production from bird flu, Benson said.

USDA has

launched a program

to compensate farmers with sick cows for 90% of lost milk production per cow as the agency seeks to encourage farmers to test herds and report infections.

USDA, on its website, reported two positive herds in Oklahoma. Benson said the confirmed positive sample is from one Oklahoma dairy that has two separate barns.

Oklahoma's agriculture department thinks USDA received the dairy's samples in the first week of July, Benson said. The herd has fully recovered, and Oklahoma has not received reports of other possible infections, the state said.

Oklahoma has made

protective gear

available to dairy farmers and asked dairies to increase safety and security measures, state veterinarian Rod Hall said. There is no mandatory testing of cows in Oklahoma, according to the state agriculture department.

Colorado reported four

confirmed bird flu infections

in poultry workers and is checking on the status of a fifth suspected case, health authorities said on Sunday. (Reporting by Brijesh Patel in Bengaluru and Tom Polansek in Chicago; Editing by Rod Nickel and Leslie Adler)