The US has identified its fourth human case of bird flu linked to an outbreak among dairy cattle.
A fourth individual in the United States has been diagnosed with H5 bird flu amid an ongoing outbreak affecting dairy cattle nationwide.
On Wednesday, the Colorado Department of Public Health and Environment confirmed the state’s first human case of H5 avian influenza linked to the multistate outbreak among dairy cattle. This marks the fourth such case reported nationally, following two cases in Michigan and one in Texas.
Colorado has seen significant impact, with more than a quarter of its dairy herds reporting bird flu cases, according to state health department data. Among all affected states in the past month, Colorado has recorded the highest proportion of cases, accounting for 40% of the total.
The infected individual in Colorado exhibited mild symptoms, primarily presenting with conjunctivitis (pink eye), and had direct exposure to avian flu-infected dairy cattle while working at a farm in northeast Colorado. Upon testing positive, the person was promptly treated with the antiviral drug oseltamivir and has since recovered, as confirmed by state health officials.
Dr. Rachel Herlihy, state epidemiologist at CDPHE, emphasized that while avian flu viruses are spreading among animals, they are not currently adapted for human-to-human transmission. She underscored the importance of precautions for individuals regularly exposed to infected animals, noting that the last human case of H5N1 in Colorado occurred in 2022 in a person exposed to infected poultry.
Previously identified human cases in this outbreak also reported eye-related symptoms, similar to conjunctivitis, while one case described respiratory symptoms such as cough, congestion, sore throat, and watery eyes. None of the affected individuals had contact with each other, all having worked closely with cattle, suggesting potential cow-to-human transmission of the virus.
At the national level, the Centers for Disease Control and Prevention (CDC) continues to monitor the situation closely using flu surveillance systems to track H5N1 activity in humans. The CDC maintains that the overall health risk to the general public remains low despite the recent case in Colorado.
The CDC has reiterated its recommendation for dairy workers to use personal protective equipment to minimize the risk of infection. Additionally, the US Department of Agriculture is providing financial support to farms with infected animals to ensure workers have adequate protection. Ongoing research aims to understand transmission dynamics from cows to humans in these instances.
Dr. Nirav Shah, principal deputy director of the CDC, assured that the public health system is well-equipped with ample H5-specific tests to manage the current outbreak, with additional tests becoming available in the coming months. The situation underscores the need for vigilance and adherence to recommended precautions among those with potential exposure to infected animals, reinforcing public health efforts to mitigate further spread of the virus.