US health officials have confirmed four new cases of bird flu in poultry workers in the state of Colorado . The Centers for Disease Control & Prevention (CDC) said there is also a fifth person with symptoms who is undergoing testing, with the case yet to be confirmed. It marks the eight case of bird flu to be detected in the US since March.

1.8 million chickens killed in US as bird flu vaccinations begin in Europe Fourth human case of bird flu linked to outbreak in US cows confirmed Health officials said the poultry workers who tested positive reported mild illness, including conjunctivitis, fever, chills, coughing and sore throat. The workers were culling poultry at a farm in northeast Colorado and all had direct contact with infected birds.

The CDC said the risk to the public from the outbreak remains low. It said a team of nine people, including epidemiologists, veterinarians and clinicians, is on the ground in Colorado to assess the outbreak and the human cases. Earlier this year there were cases among dairy farm workers in Michigan, Texas and Colorado.

As of Friday, the H5N1 virus has been confirmed in 152 dairy herds in 12 states, according to the U.S. Agriculture Department.

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