Concern about bird flu seems to be growing steadily locally and nationally. Here in Pennsylvania, in a roundtable last week, Governor Josh Shapiro said the commonwealth is “in crisis mode when it comes to avian influenza,” adding that “Pennsylvania is really sadly at the epicenter of this.” Among other steps, Shapiro’s administration is working with bird flu specialists from the U.S. Department of Agriculture, asking the federal government for regulatory changes to allow more veterinarians to work with the state veterinarian to diagnose more cases, urging the federal government to support creation of an avian flu vaccine and allocating $6 million to create a veterinary blood testing lab in Western Pennsylvania to improve surveillance.
Pennsylvania also set aside $60 million in recovery funds for farms that need to cull flocks to slow down spread, and some N.J. parks have been closed as 1,100 dead or sick wild birds were reported in N.J. between Feb. 14 and 16.
Bird flu in humans has been rare — about 70 cases since 2024. Cases are usually mild, although there was a human death from the H5N1 strain in Louisiana in January. Nationwide, 9.65 million birds have been affected, the USDA reports. Thirty elephant seals have died in California since last week from bird flu. (The same H5N1 virus that causes bird flu previously killed tens of thousands of seals in the Southern Hemisphere.)
According to the USDA, there are no current human cases of avian flu, but a rising number of dead wild birds and infections in other animals are raising questions about whether this is likely to spillover to humans in our region in the near future.
Here to sort out what we know, and steps to minimize health risks, is Thersa Sweet, PhD, a teaching professor in the Dornsife School of Public Health. Sweet has taught and published research on a range of topics in epidemiology, biology, virology and pathology.
What is avian influenza? Is it new to the United States?
Avian influenza is not a new type of influenza. Avian influenza typically infects wild and domestic birds. Often wild migratory birds show no signs of disease, but these viruses can be particularly pathogenic in domestic poultry. In fact, these viruses are so pathogenic in domestic poultry that if cases are found in a flock, typically the entire flock is culled to stop the spread of the virus to nearby flocks or farms. There have been outbreaks seen in domestic poultry both globally and in the U.S. for many years. There have been cases of avian influenza in humans, but these are rare. In addition to being rare, typically, humans who are infected with avian influenza are infected from birds, often farm workers, and then are “dead end” hosts for the virus. Avian influenza viruses have historically had a limited ability to spread from human to human. In the past couple of years in the US, there have also been cases of avian flu spreading from dairy cows to human farm workers. These cases are concerning as infection in cows is a relatively newly discovered phenomenon as is spread to humans from the infected cows. However, these cases have been “mild” usually resulting in “pink eye” due to milk entering the workers’ eyes during the milking process.
As there are no human cases, what’s your take on the response from the commonwealth?
I agree that this should be a concern for the state. Even if we ignore the potential for human cases, there is a large monetary cost to infections in over 7 million birds. Farmers are at risk of losing income from these lost birds as this disease in domestic poultry is often quickly fatal and all birds in an infected flock are typically culled to stop the spread to nearby flocks. This also may potentially affect the cost of eggs and/or meat from the animals.
Surveillance should also be performed on dairy cows as it has now been shown that avian flu viruses from migratory birds can infect cows and nationally there have been cases of bird flu in humans (not too severe – primarily “pink eye”) from milking cows.
As for creating an avian flu vaccine – I would like more information about what the government can require and how amenable US farmers would be to this. An avian flu vaccine has been used in the past by China to stop an H7N9 in 2017 and was wildly successful in stopping infections not only in birds, but in humans. There had been considerable concern by 2017 as there had already been five waves of H7N9 flu outbreaks in humans in China, and the one in 2017 was larger than in previous years and showed some person-to-person spread. They used a new avian flu vaccine in domestic poultry and did not have any more human cases of disease. There seems to be pushback from some farmers in the US about vaccinating domestic poultry. Some of the issue is around the ability of farmers to export chickens that have been vaccinated. Some countries use a test that cannot differentiate between actual infection and previous infection or vaccination, so vaccinated chickens cannot be exported. I would like to hear from an expert about this, possibly from the USDA.
In addition to the need to protect the health of humans and animals, there are real financial costs and quality of life concerns, right?
Yes, this is quite concerning. In addition to the cost to farmers for lost animals and lost egg production, it may increase the price of eggs due to a decrease in egg production. Influenza viruses are highly mutable, which is why we need a new flu vaccine for humans every year. If the avian flu mutates and now causes disease in wild birds, there could be a huge issue going forward.
What is the current risk of spread to humans?
While I will not say there is no risk of spread of avian flu to humans, there is a low risk at this point. However, people who have poultry, whether it is a large farm or a backyard flock, need to practice biosecurity measures to protect their flocks from these viruses and then also themselves. People should not be raising poultry, pigs or cows unless they know how to protect them from avian influenza and practice biosecurity. The USDA site has more information about this.
What can people do to protect themselves and their pets?
I recommend that pets be kept indoors if at all possible. Those who raise chickens, pigs, cows or other animals that can be infected with these viruses should be following strong biosecurity precautions as recommended by the USDA. I also strongly recommend against drinking raw milk. It has been shown that cows have plenty of receptors on their udders for avian influenza viruses. This is how these viruses are spreading from cow to cow. Therefore, the virus ends up in the milk. I also recommend against giving pets raw pet food. Cats can be infected with avian influenza and this can be lethal. There is also the concern about potential spread to pet owners.
Seems like most human cases have been mild and resolve on their own. Is that encouraging, or are you still worried?
While I am not highly worried about this, I am paying attention. Yes, most cases of avian influenza in humans have been mild and these viruses do not seem to spread from human to human well. However, given how highly mutable influenza viruses are, I do think we need to pay attention to infections in animals and in humans. Continual surveillance in domestic poultry, cows, pigs, wild animals, pets and humans is absolutely necessary.
Reporters interested in talking with Sweet should contact Greg Richter, an assistant director of media relations, at 215-895-2614 or gdr33@drexel.edu.
