“Alarm Bells Ring: Health Experts Sound Off on the Resurgence of Bird Flu”

Last week, there was a fatality resulting from the bird flu. What is the current status?

Andy Pekosz: We’re observing indications that this virus is increasingly affecting humans. An individual in Louisiana contracted the virus, apparently after interacting with a flock of chickens that had been exposed to wild birds. Both the chickens raised by this person and the wild birds were found deceased. The individual who experienced exposure to H5N1 required hospitalization and ultimately succumbed to the illness.

If that wasn’t alarming enough, when CDC researchers analyzed samples from this person, they discovered that the virus had begun to evolve at two specific locations known to be crucial for H5N1’s adaptation for better replication in humans. This is similar to a situation that occurred around two months ago in British Columbia. We need to intensify our initiatives to reduce H5N1 infections in humans to minimize the chances for this virus to learn how to efficiently infect humans.

Does the flu season exacerbate the situation?

AP: On a positive note, many hospitals and regions are now extensively testing for influenza. This enhances our monitoring capabilities, as discovering influenza-positive cases allows us to identify whether they’re caused by seasonal flu or H5N1. Hence, our testing is becoming more comprehensive.

The concern lies in the fact that if an individual contracts both seasonal influenza and H5N1, these viruses could exchange genetic material, leading to the emergence of a virus more adept at infecting humans. This process, called reassortment, is quite rare, but historically it has led to the influenza viruses responsible for the last three human pandemics.

Are we at a concerning threshold with this virus?

Meghan Davis: We are, particularly if you are a domestic cat. When this virus infects felines, it induces exceedingly severe illness along with extremely high mortality rates.

There have been multiple product recalls associated with H5N1 infections, not only involving contaminated raw milk but also raw pet food products. If individuals are exposed to the virus through their pets, it could represent a different type of exposure than what we’ve previously observed. For those who are immunocompromised, this might lead to distinct mutations in the virus or different clinical presentations of disease.

We still face a significant outbreak in cattle.

MD: Yes, even though California, the top dairy-producing state and the epicenter of the current outbreak, is beginning to manage the situation. We’ve observed a decline in new herds being identified. Nevertheless, we still have more than 300 herds affected nationally.

AP: It’s essential to highlight that the two serious human influenza cases—the one in British Columbia and the one in Louisiana—involve H5N1 viruses, although they represent slightly different strains than those infecting dairy cows.

H5N1 is an extremely dynamic virus. Many variants are circulating among various animals and birds, presenting an escalating threat regarding spillover and the potential for a pandemic.

Should we be worried about human-to-human transmission?

AP: Absolutely. The mutations identified in infected individuals alone likely won’t enable the virus to spread between people. We have yet to see any evidence of transmission, but more extensive surveillance in broader at-risk populations is necessary. While the virus can induce mild illnesses in certain contexts, it suggests we may need to conduct more comprehensive testing to determine how much of that mild disease arises from these spillovers into humans.

MD: Should we begin to notice ongoing human-to-human transmission, that would be a significant alarm and a cause for greater concern beyond the usual “high threat level” for public health experts. This would imply that the general population, outside of these high-risk groups, would need to exercise increased caution.

It’s also vital to acknowledge that sustained animal-to-animal transmission has been observed, not solely in birds, but among mammals as well, and not just dairy cattle. Studies have indicated that ferrets can transmit the virus to other ferrets, which is another species particularly vulnerable to influenza viruses. This provides the virus with more chances to “fine-tune” mutations and to select for strains better suited for mammalian transmission.

What proactive measures can we take to prevent a pandemic?

MD: We should undoubtedly enhance animal surveillance, and we are beginning to do so. For dairy cows, there exists a method for mass testing using bulk milk tank tests, allowing for assessments of pooled milk from hundreds of cows for H5N1. Upon obtaining a positive result, we can trace back to the original farm to identify potentially infected cows. This is crucial for preventing the spread from one dairy cow to another, whether through direct cow movement, personnel, equipment, or other pathways.

We suspect that, given the proximity of farms to each other, other animals could play a role in transmission. While this is reasonable for wild birds, we require further surveillance of animals like field mice, some of which have been confirmed infected in Colorado. Grasping the ecology of this disease is essential.

Analyzing other species will also be critical. We know that goats are susceptible, so enhancing our surveillance in small ruminants could be the next focus. The more we learn about the virus’s presence in animals, the better we can contain its spread within the species we raise for food, and thus identify which individuals are at the highest risk of exposure.

Is the general public at risk?

AP: We understand that the documented cases of infection have arisen from exposure resulting from work on dairy farms or poultry facilities, or contact with backyard poultry flocks or infected wild birds. While we have yet to confirm a human case of H5N1 from raw milk, numerous examples exist of animals contracting it. If you reside in those areas, heightened caution is advised, and in the case of raw milk, it should simply be avoided.

Should individuals handling poultry wear masks or thoroughly wash their hands to prevent infection?

MD: Great care should be exercised if you have any interactions with livestock. In the early stages of infection, birds may not exhibit many symptoms, and numerous pathogens can be transmitted from poultry, which is why I consistently recommend practicing excellent hygiene when engaging with them.

Observing local developments is vital.

by visiting the USDA webpage could also assist you in making choices based on the existing threat in your region. Currently is the time when individuals [who are in contact with poultry] should remain vigilant and alter their actions if it’s prevalent in the vicinity. 

If you maintain backyard poultry, there are resources at your disposal. The USDA and several land-grant universities with extension programs offer numerous materials on how to safeguard your birds and your health while working with them. 

What signs would suggest to you that this is becoming a more significant danger to humans?

AP: The essential aspect is discerning whether the virus currently present in dairy cattle will acquire mutations that enable it to become more transmissible among mammals. We understand that milking machinery for dairy is spreading the virus from one animal to another. If the virus alters its transmission method and evolves into a respiratory pathogen in dairy cows, that would serve as an additional indicator that this virus is evolving and presenting a greater risk to the human population. 

What effects does all of this have on the dairy sector?

MD: To be frank, this is a crucial crisis. Significant expenses are involved in breeding and maintaining livestock. We still do not know what the long-term health repercussions will be for the animals that were afflicted. While they can survive, many may experience reduced productivity for years, potentially throughout the remainder of their lives. 

Moreover, the dairy industry has not had to confront this level of biosecurity requirement in a long while. Most of the barns—which are costly to construct—in warmer regions are dry lot dairies, meaning they have roofs but no walls, allowing birds, cats, mice, and other creatures to enter. Redesigning these farms could take a considerable amount of time. With over 25,000 decision-makers in the dairy production sector, and the numerous approaches to raising dairy cattle, there will not be a universal solution that fits all.

 

This interview was condensed for length and clarity by Morgan Coulson, an editorial associate in the Office of External Affairs at the Johns Hopkins Bloomberg School of Public Health.

 

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