The H5N1 bird flu virus has spread to dairy cows in the United States, raising concerns about its spread to humans.

Since 2022, bird flu in the U.S. has infected 168 dairy herds, seven people who were exposed to poultry, four people who were in close contact with infected cattle, more than 100 million chickens and over 9,500 wild birds.

The following is a timeline of the current outbreak in the country:

HEALTH EXPERTS RAISE CONCERN OVER THE DISPOSAL OF INFECTED POULTRY BIRDS AS AVIAN FLU SPREADS

The U.S. Centers for Disease Control and Prevention on Friday confirmed two additional cases of bird flu in Colorado poultry farm workers in addition to four previously confirmed human cases in the state this year.

The health agency also said preliminary results from blood samples collected from 35 people who work in dairy farms in Michigan with infected herds did not show neutralizing antibodies specific to the H5N1 virus, an indication that the disease was not present in a wider group.

Oklahoma became the 13th U.S. state to detect bird flu in dairy cows, the U.S. Department of Agriculture confirmed.

The U.S. government awarded $176 million to Moderna MRNA.O to advance development of its bird flu vaccine.

Wyoming became the 12th state to report an infected dairy herd.

Minnesota became the 11th state to report an infected dairy herd.

Bird flu outbreak in dairy cows expanded to a tenth state as Iowa reported its first infection in a herd.

A third U.S. dairy worker tested positive for bird flu in 2024 after exposure to infected cows, and was the first to suffer respiratory problems. The infection was the second human case in the state of Michigan.

Another 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.

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

Colombia restricted the import of beef and beef products coming from U.S. states due to bird flu in dairy cows.

The U.S. government said it will require dairy cattle moving between states to be tested for bird flu.

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.

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.

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

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.

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.

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.

Egg producer Cal-Maine Foods CALM.O said it had temporarily ceased production at a facility in Kansas after some of the flock tested positive for avian flu.

Arkansas, a major U.S. chicken producer, reported its first outbreak of lethal avian flu in a commercial poultry flock in a year.

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.

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.

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.

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.

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.

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.

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.

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.