In coordination with state health departments in Michigan and Colorado, the Centers for Disease Control and Prevention (CDC) tested blood from people who were exposed to dairy cows with H5N1 bird flu infection, also known as highly pathogenic avian influenza (HPAI).
Eight of the 115 people tested (7% of participants) showed evidence of recent H5N1 virus infection. Only four of those eight remembered feeling sick or had symptoms.
All eight of the workers reported cleaning the milking parlor as a regular task. Only one individual said they worked with cows known to be infected with H5N1. None of the workers with signs of infection reported using the recommended personal protective equipment (PPE), and the use of recommended PPE was low among all 115 workers tested.
The blood tests reveal H5N1 was present in more individuals than what was known, as previously only two dairy workers in Michigan and one in Colorado had been confirmed through other detection methods.
Additional confirmed cases of H5N1 in dairy workers in the U.S. include one in Texas and 21 in California.
The study was conducted to help the CDC better understand the infection rate of farm workers frequently exposed to H5N1-infected dairy cows and to improve protection measures.
With these findings, the CDC has updated its interim recommendations to improve and clarify guidance to farm workers and their employers about what PPE to use and how best to use it to protect themselves and prevent the spread of the virus.
Data from the survey helped identify settings and activities that are higher risk for transmission of H5N1. With this, the CDC was able to better prioritize its PPE recommendations, tailoring them to different work tasks and settings.
The CDC also updated its recommendations for testing and for offering oral antiviral medications. It suggests that asymptomatic workers with high-risk exposure, especially those that didn’t wear PPE, be provided with appropriate testing and be offered oseltamivir (Tamiflu), an FDA-approved oral influenza antiviral, for post-exposure prophylaxis of H5N1.
The study highlights the need for employers and public health to strengthen prevention activities to better protect farm workers from this infection.
The risk of infection with H5N1 virus among the general public remains low.
