H5N1 virus particles (yellow) grown in epithelial cells (blue). Credit: CDC and NIAID / Wikimedia Commons
Bird flu continues to spread across the United States and behave in uncanny ways.
Last week, a Louisiana resident became the first human in the country to die from the H5N1 influenza virus, after being hospitalized with severe illness. The patient, who was older than 65 and had underlying health conditions, contracted the infectious disease from exposure to wild birds and a backyard flock of chickens, the Louisiana Department of Health reports.
Experts monitoring and investigating the virus say the news is not a reason to panic, and the risk remains low to the public. But the rapid rate at which H5N1 is infecting not only wild birds and poultry but also cattle and other mammals, including humans, raises concerns for infectious disease experts, who say that additional tracking and preventive measures are necessary: If the virus mutates in a way that allows it to pass from one human to another, experts fear it could become an epidemic or pandemic.
To prevent the spread of avian flu:
- Avoid raw milk products and raw or undercooked meat products, including eggs; consume pasteurized milk and pasteurized milk products only
- Do not touch or handle dead or dying birds, animals, and mammals
- Protect your pets: Keep cats indoors, keep dogs away from areas with migratory birds, and avoid feeding raw milk and raw meat pet food diets
- Contain backyard chickens and change your clothes and wash your hands after visiting the coop
“At this point, we’ve seen no evidence of human-to-human transmission,” says Johns Hopkins molecular epidemiologist and environmental microbiologist Meghan Davis. “Signs indicate that it could happen, but no one knows for certain whether it will or not.”
Davis, who spent more than a decade working as a veterinarian, is an associate professor of environmental health and engineering at Johns Hopkins’ Bloomberg School of Public Health, with joint appointments in the School of Medicine. She sat down recently with the Hub to discuss the evolving bird flu situation and share advice for the public on how to stay safe.
H5N1 has been on our radar for a while. What makes the virus newly concerning?
Usually, when we see an outbreak, it flares up and then goes away. The challenge we’ve had with this strain of H5N1 is that it’s had a staying power not seen in prior avian influenzas, [along] with a plot twist earlier this year when the virus got into dairy cows. This isn’t typical for avian influenzas.
In cows, H5N1 infects the mammary gland, so milk is something we’re really worried about now. Another unusual factor, however, is that the virus isn’t just infecting cows but also other mammals, from foxes and bears to field mice, squirrels, and even domestic cats. In South America, the virus caused a high number of marine mammal deaths, which is also unusual.
The adaptability of this virus and its staying power—and now this new way of being exposed through milk from cows—means it’s creeping closer and closer to the threshold of concern from a pandemic potential perspective.
What symptoms is the condition causing? Are there differences between infections caused by cows or birds?
H5N1 contracted from wild birds and backyard flocks tends to cause more severe respiratory symptoms and illness. This is more [akin] to older strains of bird flu we’ve seen, which have a fatality rate in humans of as high as roughly 50%—not a number anyone wants to hear. But it does mean that human exposure to the virus could come with tragic consequences.
People who work with dairy cows and poultry infected with the dairy-associated genotype often present with upper respiratory symptoms, fever, and conjunctivitis, [an infection or inflammation of the eye that causes swelling and redness and can be itchy and painful]. It’s a milder form of illness more like the [seasonal] flu, although conjunctivitis can be the most bothersome symptom, and it can be severe.
The [working] hypothesis is that dairy farmers get splashes of milk in their eyes, or they touch their eyes, while working with cows in the milking parlor. Because they’re milking cows at face heigh