Unrecognized Cases of H5N1 Bird Flu Are on the Rise
H5N1 bird flu might be infecting more individuals than we're aware of. Recent studies conducted by the Centers for Disease Control and Prevention reveal that around 7% of monitored dairy farmers in Michigan and Colorado have tested positive for antibodies related to the virus.
Since 2022, highly contagious avian influenza A strains of H5N1 have started to infect mammals beyond birds. This year, H5N1 has spread widely among dairy cattle and other livestock in the United States. As of now, there have been 46 verified human cases of H5N1 in the U.S., with the majority (excluding one incident) believed to have originated from cattle or poultry. These new findings, released on Thursday in the CDC’s Morbidity and Mortality Weekly Report, do not imply that H5N1 is now spreading among people, but they do signal the need for increased vigilance to avoid such a scenario.
The CDC collaborated with health officials in Michigan and Colorado (both experiencing dairy cow outbreaks) to conduct interviews and blood tests on local dairy farm workers. Of the 115 workers who underwent blood tests, eight workers were found to have H5N1 antibodies—an indication of past infection. However, only four of these workers recalled having recently fallen ill.
Fortunately, these unnoticed cases do not suggest that the virus has mutated to affect humans directly yet. The infected workers had reported milking cows or cleaning the milking parlor recently, and of the four sick cases, all had worked on farms where H5N1 had been detected in cows nearby. This implies that the virus had likely transferred from cows to these workers. There have been no indications of unusual flu activity in the U.S. lately, further reducing the possibility that H5N1 has spread beyond these specific instances.
However, H5N1 outbreaks in dairy cows have occurred in 48 states this year, and thousands of workers have likely been exposed to these infected cows. Therefore, the confirmed human cases discovered so far are likely a significant underestimate of the actual impact.
The more these viruses spread from birds to mammals, the higher the probability of them evolving into strains that can easily infect mammals in general. The more opportunities H5N1 has to infect humans, the higher the likelihood of a strain inevitably acquiring the right mix of mutations, transforming it into a rapid-spreading, deadly pandemic in humans. Consequently, the harder we are at finding these early cases, the harder it will be to prevent H5N1 from becoming a significant issue.
The CDC researchers assert that additional measures are necessary to track and prevent the spread of H5N1 on dairy farms.
“The findings underscore the necessity of active monitoring of exposed workers and testing to detect and address HPAI A(H5) infections, including those with extremely mild symptoms,” they wrote. “These endeavors should accompany farmworker education about infection risks and prevention strategies.”
Down the line, advancements in science and technology could provide us with tools to detect H5N1 in its early stages, potentially reducing its impact on human health. In the future, a stronger focus on public-private partnerships in the field of health research could accelerate the development of effective vaccines or treatments against emerging avian influenza strains.
