Health News

Humans at Risk, New Bird Flu Strain Targets Eyes

Humans at Risk, New Bird Flu Strain Targets Eyes | Credits: NBC News

United States: In recent times, the behavior of avian flu, specifically the strain H5N1, has been rather peculiar. This variant of the highly pathogenic avian influenza virus has been proliferating among dairy cows in at least nine states within the United States.

Remarkably, these cows exhibit remarkably elevated levels of the virus within their milk. Initial findings suggest that the transmission is facilitated through tainted milking apparatus, though alternative modes of dissemination remain plausible.

Notably, several felines that ingested raw milk from infected cows manifested neurological symptoms and perished. However, the process of pasteurization appears to effectively deactivate the H5N1 virus.

Over the past few weeks, three instances of human infection by this virus have been documented, all involving dairy laborers who had direct contact with ailing cows. In each case, the afflicted individuals presented symptoms consistent with ocular infections known as conjunctivitis. The most recent occurrence, reported in Michigan, also exhibited respiratory symptoms akin to those of typical flu infections.

The prevailing belief is that these workers were likely exposed to the virus via contaminated milk—whether through manual contact and subsequent ocular transmission or through milk droplets (or even minuscule aerosolized particles) emanating from a cow’s udder or milking equipment.

Ron Fouchier, deputy head of the viroscience department at Erasmus University Medical Center Rotterdam, expressed astonishment at the extensive dissemination of the virus through milking machinery, remarking on its novelty and the substantial viral loads present in raw milk.

However, the question arises: Why does H5N1 induce ocular infections in humans, and what are the prospects of broader transmission leading to a potential pandemic?

Contrary to popular belief, occurrences of avian flu precipitating conjunctivitis are not unprecedented. A significant outbreak of H7N7 avian flu in Dutch poultry in 2003 resulted in 89 confirmed human cases, predominantly featuring conjunctival complications. Notably, the recent spate of H5N1 outbreaks in cows and subsequent human infections mirror patterns observed with H7N7 viruses, albeit to a lesser extent.

The mechanism by which H5N1 induces ocular infections in humans is presumed to involve viral binding to receptors within the conjunctiva—the translucent membrane enveloping the inner eyelid and the sclera. While prevailing wisdom posits a dichotomy between avian flu viruses, which purportedly favor avian receptors, and human seasonal flu viruses, which target human respiratory tract receptors, recent research indicates a more nuanced interplay between these receptor types across both avian and human populations. Consequently, the predilection of H5N1 for avian receptors in the human eye elucidates its propensity to induce ocular infections.

The possibility of H5N1 ocular infections progressing to respiratory involvement underscores the potential for severe, systemic complications. Despite scant evidence of current human-to-human transmission, heightened cross-species transmission and subsequent human infections could precipitate viral adaptation conducive to enhanced infectivity and transmissibility.

Yoshihiro Kawaoka, a virology professor at the University of Wisconsin–Madison’s School of Veterinary Medicine, voiced apprehension regarding the potential spill over of the virus to humans, poultry, and other animals, given the substantial viral loads detected in infected cow milk.

Seema Lakdawala, an associate professor of microbiology and immunology at Emory University School of Medicine, emphasized the susceptibility of milking parlors to viral dissemination among workers. She underscored the imperative of implementing comprehensive measures to mitigate transmission risks, advocating for universal access to personal protective equipment (PPE) among dairy workers and veterinarians. Furthermore, Lakdawala stressed the importance of vaccination campaigns targeting these at-risk populations.

Efforts to contain the spread of H5N1 necessitate a multifaceted approach encompassing stringent biosecurity measures, enhanced surveillance, and proactive vaccination initiatives. The imperative to pre-empt potential pandemic scenarios underscores the urgency of collaborative action among stakeholders across the agricultural, public health, and veterinary domains.

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