Human cases of bird flu have been confirmed to be occurring undetected in the United States. Cases of the highly pathogenic avian flu have been undetected in humans, as evidenced by blood samples from 115 dairy workers in Michigan and Colorado. Antibodies from the extremely virulent strain of H5N1 were detected in the blood of 7% of individuals who were tested between June and August 2024 by researchers from the US Centers for Disease Control and Prevention (CDC). The positive news is that this indicates that the majority of individuals who have contracted avian flu thus far have not experienced a significant amount of damage. It is possible that only mild symptoms were encountered by half of the individuals who had virus antibodies in their bloodstream, as they did not report feeling unwell.
Nevertheless, researchers are apprehensive that the virus’s potential to mutate into more lethal variants is increased by its unchecked spread, despite the fact that the current danger to public health is still low. In Cambodia, the disease’s virulence has undergone a transformation, resulting in the deaths of at least three patients. This strain of avian flu, which was transmitted from poultry, is a hybrid between 2.3.2.1c and 2.3.4.4b. A preprint study indicates that this hybrid contains mutations that facilitate airborne transmission and infection of mammals.
Close monitoring indicates that the Cambodian outbreak is fortunately contained, and no human-to-human transmission has been identified. Canada has recently disclosed its initial human case of bird flu. The patient, an adolescent, is currently hospitalized in critical condition and possesses a mutated strain of the virus that was identified in the US dairy cattle outbreak. A mutation in a gene that is recognized as enhancing the virus’s capacity to infect humans is evident in the initial genetic sequencing.
The Canadian case appears to be an isolated incident at this time; however, these alarming examples underscore the vulnerability of viruses to fluctuating risks, underscoring the necessity of meticulous outbreak management and close monitoring. Currently, there is only one confirmed case of avian flu that has no known animal origin, which has raised concerns that the virus may have spread from person to person.
The dairy laborers in the United States who exhibited symptoms of previous infection were all involved in the milking of cows or the cleansing of the milking parlor. Individuals who reported experiencing illness reported symptoms such as a fever, sore throat, congested nose, congestion, diarrhea, or migraines. In addition, they reported red, draining, or irritated eyes.
In their report, CDC health scientist Alexandra Mellis and colleagues state that “none of the workers with HPAI A(H5) virus antibodies reported using the personal protective equipment (PPE) recommended for working with HPAI A(H5)–infected animals, and use of recommended PPE was low among all workers.”
The CDC is intently monitoring the situation. The highly virulent avian flu has infected over 400 dairy herds in 48 states, in addition to poultry outbreaks. The necessity of ongoing, rigorous surveillance to prevent the further spread of the current outbreaks in animals and to improve the management of them is underscored by researchers and healthcare professionals.
Mellis and colleagues explain that these findings underscore the necessity of enhanced outreach to employers and employees regarding the risk of infection associated with working with dairy cattle infected with HPAI A(H5) viruses, as well as the implementation of infection prevention measures such as personal protective equipment (PPE). They also emphasize that the outreach must be culturally appropriate, as a significant number of the workers in the most recent report are Spanish speakers.
Authorities worldwide are encouraging individuals to report sightings of multiple ill or deceased birds and to maintain good hygiene when interacting with animals. Drowsiness, a lack of coordination, the inability to stand or fly, moving in circles, a head inclination, and/or a lack of coordination are all indications of infection in animals.
In the United States alone, the highly virulent avian flu has resulted in the culling of over 90 million domestic birds since 2022. In order to mitigate the disease’s effects on the critically endangered California condor, a vaccination program has been implemented; however, it is probable that numerous other species will require assistance. In the interim, researchers are simultaneously exerting significant effort to create a human vaccine.
Overall, the detection of undetected human cases of bird flu in the United States highlights the ongoing threat that highly pathogenic avian flu poses to public health. The presence of antibodies in dairy workers underscores the potential for human transmission of the virus from animals. While the current risk level remains low, the possibility of the virus mutating and becoming more lethal is a cause for concern.
The recent cases in Cambodia and Canada serve as reminders of the unpredictable nature of avian flu and the importance of vigilant monitoring and rapid response to outbreaks. Enhanced outreach and education efforts are crucial to prevent further infections and protect at-risk populations, especially those working closely with infected animals.
As the global community continues to grapple with the challenges posed by avian flu, coordinated efforts between researchers, healthcare professionals, and government agencies are essential to mitigate the spread of the virus and protect public health. By remaining alert and proactive, we can work together to address the evolving threats posed by avian flu and safeguard the well-being of communities worldwide.
