A new CDC study suggests that cases of H5N1 bird flu may occur in people who work with dairy cows … [+]
A new one CDC report showed that 7% of the dairy workers tested had indications of a previous infection with the H5N1 bird flu virus or the “bird flu virus”.
The study, conducted between June and August this year, took blood samples and interviewed 115 people who worked with infected dairy cattle in Colorado or Michigan. All workers had tasks such as milking cows, cleaning manure and moving livestock. Only a small number of workers surveyed reported wearing eye protection such as goggles (37%) or high-quality masks called respirators (21%).
8 people tested (7%) had evidence of antibodies against the virus in their blood, indicating a previous infection within the past three months. Four people interviewed recalled being sick around the time the dairy cattle they worked with tested positive for H5N1. All workers reported cleaning the parlor, while 7 out of 8 people also reported milking cows. About 4 in 10 people who did not test positive for the virus reported cleaning the milking parlour, with the authors speculating that that activity could be particularly risky for contracting the virus due to the high amounts of H5N1 in the milk of infected cows.
None of the people who tested positive for the virus wore the recommended respirators and 3 of the 8 wore eye protection. Half of those who had previously had an H5N1 infection reported no symptoms or awareness that they were ill during interviews by the research team.
As of November 4, the CDC will only report 44 confirmed cases of H5N1 in people in the US, but the new study suggests the actual number of cases could be significantly higher. 440 dairy herds in the US have been infected so far, so if the 7% of workers actually infected in the CDC study from Colorado or Michigan applies to all dairy farms, the actual number of infected workers could be hundreds or even thousands. Earlier this month, the virus was also found during wastewater research in a Los Angeles CountyThis suggests that a significant number of infections may go unnoticed.
According to the World Health Organization 903 cases of H5N1 in humans have been detected in five countries since 2003. Of these cases, 464 were fatal, resulting in a rare fatality rate of 51%. However, this is likely a significant overestimate, as people who are sicker are more likely to be hospitalized and tested for H5N1. As the new CDC study shows, some people may be infected but asymptomatic. A lot of the symptoms of H5N1 also overlaps with other viral infections such as Covid-19 and influenza, meaning people may not know they are infected with H5N1 and those with mild symptoms may not seek health care.
At this time, there is no evidence of human-to-human transmission of bird flu, although there have been some cases where no known exposure to infected animals has been found. However, each infected person gives the virus the opportunity to mutate and acquire genetic adaptations to make this possible. Human-to-human transmission is a real problem, experts say, and could signal a worsening severity of bird flu into a significant and widespread threat to public health.