(Updates with second case in dairy worker)

May 23 (Reuters) - The outbreak of H5N1 bird flu virus

has spread to dairy cows for the first time in the United

States, raising concerns about it spreading to humans through

the nation's milk supply.

Since 2022, bird flu in the United States has infected over

90 million chickens, more than 9,000 wild birds, 52 dairy herds,

one person in Texas who came in close contact with infected

cattle and another after exposure to poultry.

The following is a timeline of the current outbreak in the

country:

May 22

The

third known human case

of bird flu is confirmed in the U.S. with the infection of

a dairy worker in Michigan. It is the second case in humans this

year after the virus was detected in cattle.

April 26

Colorado became the ninth U.S. state to report an infected

dairy herd.

April 25

Colombia became the first country to restrict the import of

beef and beef products coming from U.S. states due to bird flu

in dairy cows.

April 24

The U.S. government said it will require dairy cattle moving

between states to be tested for bird flu.

April 23

The U.S. Food and Drug administration said it had found bird

flu virus particles in some samples of pasteurized milk, but

said the commercial milk supply remains safe due to

pasteurization.

April 11

South Dakota became the eighth U.S. state to find avian

influenza in a dairy herd, after the U.S. Department of

Agriculture (USDA) reported infections in North Carolina, Texas,

Kansas, Ohio, Michigan, Idaho and New Mexico.

April 4

Bird flu dairy cow outbreak widened to a dairy herd in Ohio.

April 2

Mexico's agriculture ministry said it was taking

preventative measures to increase surveillance and reinforce

inspections of U.S. livestock imports after bird flu was found

in dairy cattle there.

April 1

The second known human case of bird flu in the United States

is reported in a person from Texas who had contact with dairy

cows presumed to be infected with the virus.

The virus was detected in dairy cattle in New Mexico,

Michigan and Idaho, along with Texas and Kansas.

March 25

The USDA said samples of milk collected from sick cattle in

Kansas and Texas tested positive for avian flu, but the nation's

milk supply was safe.

Dec. 12, 2023

Egg producer Cal-Maine Foods ( CALM ) said it had

temporarily ceased production at a facility in Kansas after some

of the flock tested positive for avian flu.

Nov. 3, 2023

Arkansas, a major U.S. chicken producer, reported its first

outbreak of lethal avian flu in a commercial poultry flock in a

year.

Oct. 6, 2023

The United States detected its first case of avian flu on a

commercial poultry farm since April, in a flock of 47,300

turkeys in Jerauld County, South Dakota.

April 14, 2023

The U.S. government said it was testing four potential bird

flu vaccines for poultry, after more than 58 million chickens,

turkeys and other birds had died in the nation's worst outbreak

ever.

March 20, 2023

Some of the world's leading makers of flu vaccines say they

could make hundreds of millions of bird flu shots for humans

within months if a new strain of avian influenza ever jumps

across the species divide.

Oct. 7, 2022

Avian flu infected a commercial flock of breeding chickens

in Arkansas, widening an outbreak of the disease in the southern

region.

Nationwide, more than 47 million birds have been killed by

avian flu or culled to control its spread this year in the

nation's worst outbreak since a record 50 million birds were

wiped out in 2015.

April 29, 2022

The first known human case of H5N1 bird flu in the United

States appeared in a person in Colorado, who was involved in

culling birds at a commercial poultry facility.

March 7, 2022

More than 22 million commercially raised U.S. chickens and

turkeys have been killed since February 2022 due to outbreaks of

a highly lethal type of bird flu.

March 4, 2022

A bird flu outbreak is reported in a commercial flock of

chickens being raised for meat in Stoddard County, Missouri,

taking the spread of the virus to 10 commercial chicken and

turkey farms in four states.

Feb. 9 , 2022

The USDA reported an outbreak of highly pathogenic avian flu

in an Indiana turkey flock, the nation's first case in a

commercial poultry operation since 2020.