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A third human case of bird flu in the U.S. has been identified in a Michigan farm worker with exposure to H5N1-infected dairy cows, the .

This is the first person infected with H5N1 in the U.S. to have symptoms of acute respiratory illness, the CDC said, noting that the patient is experiencing upper respiratory tract symptoms, cough without fever, and eye discomfort with watery discharge.

Two other dairy farm workers recently infected with H5N1 -- one in Texas and another in Michigan -- had symptoms of conjunctivitis only. The new case of H5N1 in Michigan is unrelated to the previous case that occurred in that state and to the one in Texas announced in April.

The patient was given antiviral treatment with oseltamivir (Tamiflu) and is isolating at home; household contacts have not developed symptoms, but are being monitored for illness and have been offered prophylaxis with oseltamivir.

No other workers at the same farm have reported symptoms, and all staff are being monitored. "There is no indication of person-to-person spread of A(H5N1) viruses at this time," the CDC stated. The agency confirmed that the risk to members of the general public who do not have exposure to infected animals remains low.

"This third case does not alter CDC's overall risk assessment, i.e., the risk of avian influenza for the general public, which remains low right now," Nirav Shah, MD, JD, principal deputy director of the CDC, said in a call with reporters. "That said, within any risk assessment, there's a spectrum, and this case highlights the elevated risk of H5 infection, particularly for individuals who have contact -- particularly unprotected contact -- with [infected] animals."

The recent cases of H5N1 highlight the growing importance of personal protective equipment (PPE) in the latest bird flu outbreak for at-risk individuals, Shah emphasized. "Previously, we focused on the importance of eye protection, given the conjunctivitis in the first two cases, but this case also underscored the importance of barrier protection, things like masks and other forms of protection."

The CDC began in May for farm workers and other people exposed to potentially infected animals or materials, such as raw milk. "Uptake has been mixed," Shah noted, adding that there has been an increased demand for goggles and other forms of PPE in some jurisdictions.

The U.S. Department of Agriculture also announced the final testing results of 109 meat samples from culled dairy cows. No viral particles were detected in 108 of 109 meat samples, but as previously announced, H5N1 viral particles were detected in muscle samples from one cow. That animal did not enter the food supply.

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