Although the H5N1 strain of bird flu (also called avian influenza) has been circulating in the United States since 2022, many health experts are concerned about the accelerating speed of transmission and the growing risk of a viral mutation that could increase the threat to humans.
Is now the time for the general public to start worrying about bird flu’s pandemic potential?
Public Health Risk Remains Low
But there is cause for concern. “We have seen ongoing and increasing spillover from both poultry and dairy cattle into humans. Additionally, we have also seen new genotypes [virus subtypes with genetic variations] spilling from birds to cattle. The threat is increasing,” says Abraar Karan, MD, MPH, a postdoctoral fellow in infectious diseases at Stanford Medicine in California.
Mutating subtypes of the virus include a H5N9 subtype at a duck farm in California, and the H5N1 D1.1 genotype reported at dairy farms and in one dairy worker in Nevada, says Benjamin Anderson, MPH, PhD, an assistant professor in the department of environmental and global health at the University of Florida in Gainesville.
What does all this mean? The probability that the virus could further change and adapt to humans continues to grow, says Dr. Anderson.
This doesn’t mean that people should panic, but it is good to be aware of the situation in your area, he says.
Most People Don’t Need to Change Their Routine Because of Bird Flu
Because right now the virus has spread only to people who have close contact with infected animals, the risk to the general public is still considered very low.
“Unless you’re a farm worker and around livestock, there’s really no need to make drastic changes to your daily routine,” says Albert Shaw, MD, PhD, a professor of medicine in infectious diseases at Yale School of Medicine in New Haven, Connecticut. People with their own backyard poultry flocks, though, should take precautions against bird flu, Dr. Shaw says.
“If you are in a group with higher exposure risk, you should take additional precautions to protect yourself. Never touch a dead animal, and if you notice an animal with unusual signs of illness, seek professional care from a veterinarian and/or your state agencies,” says Anderson.
What About the Bird Flu Virus Found in Eggs and Milk?
Right now, the best way to eat eggs safely is to cook them all the way. The CDC has always advised against eating raw eggs, and that advice hasn’t changed.
“We honestly don’t know a huge amount about eggs. Generally speaking, once bird flu shows up on a poultry farm the entire flock has to be culled. I think eggs are generally safe to eat as long as they are cooked,” says Shaw.
With regard to infections in dairy cattle, people should not consume raw (unpasteurized) milk, he says.
“It’s quite clear that the bird flu virus in dairy cattle has a predisposition to replicate to very high levels in cow’s milk and in the cow glands where the milk is produced [within the udder],” he says.
Pasteurization kills the virus, says Shaw.
What’s Being Done to Limit the Spread of Bird Flu?
The main strategy for detecting bird flu has been to test on farms, says Amesh Adalja, MD, a senior scholar at the Johns Hopkins Center for Health Security in Baltimore.
“However, that has been very constrained and limited, in part because many farmers don’t want testing done on their farms,” says Dr. Adalja.
“For poultry, when a flock is infected, it is highly lethal to the chickens very quickly,” says Anderson.
Because of this, the response taken to contain viral spread is to kill the entire flock (both the healthy and sick chickens) in order to minimize further losses for any given farm and the overall egg and poultry supply, says Anderson.
“For dairy cattle, the USDA has implemented a milk surveillance strategy where states are testing bulk milk tanks for H5N1. If a positive sample is found, then officials can trace that milk back to individual farms where they would isolate and quarantine the animals. The recent detection of H5N1 D1.1 in Nevada demonstrates that this strategy is effective when implemented,” says Anderson.
The CDC is also having human influenza cases typed to determine if H5N1 is present, and wastewater monitoring has been ongoing, he notes.
“In general, the response has not been proactive and has been late to the game, as many actions were needed months before the virus became endemic [prevalent] in dairy cattle,” says Adalja about the U.S. response.
For Now, Seasonal Flu Is a Bigger Threat to the General Public
Both Shaw and Dr. Karan agree that people who want to stay healthy should focus their efforts on avoiding the seasonal human flu.
“This is a concern because we have very high rates of flu right now,” says Karan.
