The recent incidence of bird flu detected in a dairy worker in Texas has prompted heightened vigilance among public health authorities, although experts emphasize that the virus has not exhibited increased transmissibility either among cattle or humans.
According to the Centers for Disease Control and Prevention (CDC), samples collected from the infected individual, who displayed only pinkeye as a symptom, indicate that the virus has not undergone mutations facilitating easy human-to-human transmission. Furthermore, currently available vaccines and medications continue to be effective against the virus.
Dr. Nirav Shah, principal deputy director of the CDC, emphasized in an interview on Wednesday that while the agency is treating the situation with utmost seriousness, the overall risk of avian flu to the general population remains low.
Following reports from the U.S. Department of Agriculture about cows testing positive for bird flu in several dairy farms, the CDC has collaborated with state health departments to identify and monitor individuals displaying symptoms.
Shah underscored the proactive approach taken in identifying the case in Texas, highlighting the importance of targeted surveillance efforts.
The strain of bird flu in question, known as H5N1, has been circulating among bird populations globally since late 2021, resulting in widespread infection and mortality among wild birds, as well as substantial culling of poultry on farms across the United States.
The first documented human case in the U.S. occurred in 2022, involving a prison inmate in Colorado who had worked on a poultry farm. The Texas case marks the second such instance in the country.
During a press briefing, Tedros Adhanom Ghebreyesus, director-general of the World Health Organization (WHO), stated that the organization is closely coordinating with the CDC. While acknowledging the inherent danger posed by H5N1 to humans, Tedros noted that it has not been shown to readily transmit between people.
Although the two U.S. cases have resulted in mild symptoms, H5N1 infections outside the U.S. have been associated with a high mortality rate. Recent cases in Cambodia have demonstrated this severity, with fatalities reported.
What are Bird flu Symptoms?
Bird flu, classified as a respiratory virus, has the potential to induce pneumonia in severe human cases, as outlined by the CDC. Manifestations may include fever, cough, sore throat, nasal congestion, body pains, headaches, fatigue, and respiratory distress.
While some cases exhibit mild symptoms, such as the 2022 instance in Colorado where the individual experienced transient fatigue, the recent case in Texas presented solely with conjunctivitis, commonly known as pinkeye. According to the CDC, the patient is currently in recovery, and there have been no reports of flu-like symptoms among close contacts.
However, what sets this case apart is its association with cows, sparking concerns about potential viral mutation facilitating enhanced transmission among mammals, and potentially humans.
“I don’t interpret this news as an indication of an imminent flu pandemic,” remarked Angela Rasmussen, a virologist at the Vaccine and Infectious Disease Organization at the University of Saskatchewan. “Rather, it shows the importance of heeding early warning signs. If H5N1 gains footholds in mammalian populations, it will likely undergo adaptation as viruses naturally do.”
Transmission Dynamics of Bird Flu?
An essential aspect in halting further transmission, whether within bovine populations or from cattle to humans, hinges on comprehending the mechanisms by which cows themselves disseminate the virus.
In avian hosts, the virus proliferates within the gastrointestinal tract, with infection occurring through contact with infected saliva, mucus, or feces, as stated by Rasmussen. Human transmission primarily transpires through contact with contaminated surfaces followed by touching the mouth, eyes, or nose. Inhalation of virus-laden particles in dust or droplets can also lead to infection. According to Rasmussen, the virus has an affinity for binding to receptors deep within the lungs, posing challenges for human-to-human transmission as it doesn’t readily attach to upper respiratory tract surfaces like the nose or mouth.
The fact that the Texas patient’s sole symptom was pinkeye suggests direct contact with cattle, possibly resulting in transmission through eye contact or similar means.
The manner in which cows become infected and release the virus remains uncertain. Rasmussen emphasized the difficulty in assessing the risks to individuals in proximity to cows without a clear understanding of the source of viral shedding.
Pasteurization ensures the safety of milk consumption, as affirmed by the Food and Drug Administration (FDA), as it effectively eliminates the virus. Additionally, any milk originating from an infected cow is discarded before entering the milk supply chain, ensuring further safeguards, as noted by Shah.