Avian Influenza, or bird flu, in the US has been cause for growing concerns as it spreads from wild birds to poultry and mammals. As the original strain shifts, bird flu in the US has caused new outbreaks in poultry and dairy cows, with several recent human cases in dairy and poultry workers, according to the Centers for Disease Control.

Two St. George’s University School of Veterinary Medicine professors and experts in the fields of pathology and virology, respectively, shared their thoughts on some of the pressing questions about the disease and its impact.

Hear from experts:

• Alfred Chikweto, BVM, MSc, PhD, a pathologist and an associate professor within SVM’s Department of Pathobiology; and
• Sonia Cheetham, DVM, PhD, a virologist and is SVM’s associate dean of research. She is also a professor within SVM’s Department of Pathobiology.

They discussed with SGU News the unique—and evolving—characteristics of the virus, the likelihood of it moving to human transmission in a significant way, and why a career in pathology or virology is worth considering for veterinary students.

SGU: What is unique about the 2024-25 virus outbreak?  

Dr. Cheetham: Within avian influenza viruses, there are some referred to as Highly Pathogenic Avian Influenza (HPAI), which causes severe disease with high mortality, and some that are Low Pathogenic Avian Influenza (LPAI) which do not.

An ongoing outbreak of HPAI H5N1 infection in US dairy cows, which began in 2024 has been identified. Based on genomic sequence data, there is evidence of at least two independent spillover events from birds to cows. This probably occurred due to the current extensive H5N1 viral circulation in wild bird populations.  This outbreak was surprising as H5N1 had not been reported in cattle before. Although this virus does not cause severe disease nor high mortality in cows, the alarming issue is that the virus is shed in large quantities in milk which poses a public health risk if this milk and its derivatives are consumed without proper pasteurization. Dairy herds are being monitored, and raw milk and by-products have been recalled and banned in several affected states. Pasteurized milk and byproducts are safe to consume.

Another HPAI has been identified in ducks in California, this one being from a different strain, H5N9, which resulted in the elimination of the whole flock. However, the identification of this virus may be a result of increased surveillance as HPAI outbreaks are not new.

SGU: What other types of animals are most at risk for bird flu?

Dr. Cheetham: Avian influenza viruses circulate among birds, especially waterfowl. Sporadically it spills over to domestic birds causing outbreaks. It is also possible for these viruses to infect mammals, in some cases causing large outbreaks with high mortality, for example, with marine mammals and farmed minks. Other reported species include bears, foxes, skunks, and even domestic animals such as cats and dogs. Zoo animals like tigers and leopards have also been infected. In some cases, the virus infects a new host species but does not thrive there, so the spread is stopped. However, some outbreaks have spread quickly through the new host populations. Unfortunately, the recent spillover of the H5N1 virus into domesticated cats has resulted in multiple deaths.

SGU: How can pet owners prevent infection in domestic animals like cats?

Dr. Chikweto: If they get exposed to an infected bird, possibly by eating raw meat, then they are at risk of getting infected. Keeping cats inside for now is also important—if an infected wild bird comes into your yard, then it can defecate in the yard and be a source of infection. Keep them inside.

SGU: Can animals recover from bird flu?

Dr. Cheetham: Yes, animals can recover. But some animals like domestic cats seem to be severely affected. To stop the virus from spreading to other bird flocks and to reduce the chances of it changing into new forms, infected domestic birds are usually euthanized.

SGU: Can this disease jump to humans in a significant way? Essentially, should we be concerned about another pandemic?

Dr. Cheetham: Yes, avian influenza viruses have the capacity to infect humans. The virus could evolve, drifting its phenotype by infecting humans over time. Luckily at present, these viruses do not transmit easily from human to human because the human viral receptors are not as similar to bird receptors. In the US, 68 human cases and one death have been confirmed. However, many more infections have probably gone undiagnosed due to mild, or no clinical signs present.

The most worrisome scenario is if the new avian influenza virus co-infects a human that is already infected with human influenza. In these host cells, the virus genome which is normally segmented in influenza viruses, could reassort (mix segments) to create a new virus that can easily transmit, multiply in humans and is highly virulent. For example, the H1N1 swine flu pandemic from 2009 was a result of a triple reassortment (having segments from avian, swine, and human influenza viruses).

SGU: What is the role of public health policy here?

Dr. Chikweto: Solving this type of problem requires a One Health, One Medicine concept. It requires not only veterinarians, but other professionals such as medical doctors, environmentalists, and public health officials to cooperate and respond.

Dr. Cheetham: Food animal veterinarians should test herds and follow protocols to prevent avian influenza viruses from spreading. Human doctors must consider avian influenza in diagnoses, not just assume it’s regular flu. Public health officials should focus on surveillance, education, and collaborating with industry to develop new vaccines.

The key intervention is limiting animal-to-animal transmission and preventing human spillovers. Higher case numbers increase the chances of the virus mutating through drift (point mutations) and shift (recombination and reassortment).

SGU: We are already seeing how the virus has affected egg prices in the US. What other industries could see a trickle-down effect?

Dr. Chikweto: It’s quite a devastating situation for the poultry industry. Imagine the loss that results from your entire flock being culled. You have invested so much money in that flock. And because of the outbreak of H5N1, the entire flock is euthanized. So, it’s quite a huge impact on the livelihood of farmers.

Also, if a country depends on exporting poultry products, then it is now not able to export because its products could have the disease. So economically as a country, it also has that implication and downward effect.

Dr. Cheetham: Depopulation will cause losses to the poultry industry and the smaller supply would cause poultry products to increase in price given the sustained demand for eggs and chicken, turkey, and duck meat. Farms that aren’t directly affected may still feel the impact because of market restrictions, like limits on exports or animal movement. There will be increased costs for surveillance, which involves testing, and this has historically been done by the government in US and Canada, however, it may no longer be the case.

SGU: Is bird flu present in Grenada right now?

Dr. Cheetham: We are not currently tracking avian influenza in Grenada in the vet school, although we believe we have a test that should be able to identify it from a suspected sample if needed.

Dr. Chikweto: If we start hearing that these cases are now moving from the US to the Caribbean, this will trigger us to start testing.

SGU: What is your background in your specialty? What is your day like?

Dr. Chikweto: As a veterinary student back home in Zambia, I was fascinated by the subject of pathology. It’s a specialty that keeps you thinking. You are at the front line of things before everyone knows what is going on.

For example, a dog has a tumor on the skin. The owner is concerned about that mass. Then they take the dog to the clinic. They remove that mass and submit it to our pathology lab. We look at that mass histologically with a microscope, look at what is happening to determine if it is cancerous or not. We also do postmortem examinations to determine cause of death on an animal.

Dr. Cheetham: After vet school, I obtained a PhD in virology at Ohio State University. Coursework for my PhD included veterinary and human virology as many of the viruses’ affecting animals belong to the same viral families that affect humans. I chose to remain in academia and teach virology to DVM students and do research.

SGU: Why do you love your chosen field?

Dr. Chikweto: Pathology for me is a specialty that makes me always wonder. I am passionate about it.

Dr. Cheetham: So many things! It’s relevance, the detective work, the planning, and preparedness.

SGU: What opportunities are there for a veterinary student who’s considering pathology or virology as a career?  

Dr. Chikweto: In pathology we deal with animal diseases, and how to diagnose them. We have Term 6 veterinary students rotate in necropsy for hands on pathology experiences. When they come in, at first, they are very intimidated. But as the week goes on, they tend to be more and more interested in the cases we study. Additionally, on the last day, I tell them the career opportunities, and that gets their attention. For example, in the US, there’s the American College of Veterinary Pathologists, a specialty institution that specifically trains pathologists. Students can apply for residency and get board-certified. As a matter of fact, I’ve recently mentored three students who are pursuing this field based on the experiences they had at SGU that I believe directed them into that path.

Dr. Cheetham: Virology is a very important field that is rapidly growing. Especially in the development of antiviral drugs, new vaccine approaches, and virus discovery. Virologists are also fundamental to clinical diagnosis in specialized teams in government and the agricultural and health industries. There are lots of job opportunities.

— Laurie Chartorynsky

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