In the US, bird flu started out by ravaging the poultry industry in 2022 but made the jump to cattle this year and has continued to encroach on the line that's kept avian influenza from spreading to people.
Within the past few months, the US Centers for Disease Control and Prevention's national flu monitoring system has announced two human cases of bird flu in which there wasn't a clear link to exposure to sick animals -- an adult in Missouri reported in early September and in late November, a child in California. The rest of the human cases reported in the US were mild and had clear links to contact with animals who may've been infected.
The risk to the general public (i.e. people who do not have direct contact with farm animals, especially sick ones) remains low, according to the CDC. Many infectious disease experts and scientists have steadily increased the call for more alarm and action around the current bird flu situation, especially after bird flu was first reported in a pig this fall. While again stressing the risk to the general public is low, the CDC called avian influenza spreading to a new mammal "always concerning," especially pigs as they're particularly susceptible to influenza viruses.
What's more, the spread of avian influenza is overlapping with a renewed interest in the wellness trend of drinking raw milk. In November, some raw milk sold in California was recalled because it contained bird flu virus. The fact bird flu could be found in raw milk is not necessarily surprising as raw milk doesn't go through the pasteurization process that inactivates harmful bacteria or viruses like bird flu, but it called attention to another avenue in which -- while no illnesses have been reported from it -- people could theoretically be exposed to bird flu.
As long as animals and humans live, work and gather around each other, there will be a risk of viruses mutating enough to make the jump from species to species. Fortunately, bird flu in humans so far has been rare, in part because the virus doesn't spread that easily from animals to humans, or between humans, though sporadic cases have occurred in other countries as well as in the US. As the space between the potential for human exposure narrows in comparison to the continued spread of bird flu in animals, it is increasingly important to understand the risk bird flu poses to public health and its threat of another pandemic.
Here's what to know about bird flu, or avian influenza, and what it looks like in people.
Bird flu started as a poultry and bird issue in the US but has spread to cows, which frequently have close contact with people. That increases the risk of the virus one day making the jump to humans.
What is bird flu?
In short, bird flu, aka avian influenza, is a type of flu that spreads between some animals and is currently causing outbreaks among birds and cattle in the US. Scientists are watching closely for mutations that could make it possible for the virus to spread between people, which would pose a major public health threat.
More specifically, bird flu is a disease caused by infection with an influenza type A virus, and it's either "highly pathogenic" or "low pathogenic." The current H5N1 outbreak strain among animals is highly pathogenic.
Bird flu was first detected and controlled in 1997, but it reemerged in 2003 and started spreading widely among birds.
The World Health Organization reports four types of influenza viruses: A, B, C and D. Type A viruses, which occur in humans and in different kinds of animals, are the biggest threat to public health and can cause pandemics, the WHO says. The "swine flu" of 2009's pandemic was caused by a type A virus. Seasonal flu viruses in humans are caused by type A and type B viruses.
Bird flu has been ravaging the US poultry industry for the last couple of years, resulting in the culling (killing) of millions of infected or potentially infected birds.
Is bird flu deadly? How many cases have there been in the US?
There have been 55 confirmed human cases of H5 (highly pathogenic) bird flu in the US, according to Nov. 27 information from the CDC. The vast majority of them have been in people with direct contact with sick animals, and the CDC's flu surveillance system shows no indicators of unusual flu activity in people.
Human cases remain rare, but bird flu is considered a serious threat to public health because of its historically high mortality rate -- about half the cases of bird flu H5N1 in people have resulted in death since tracking began, according to WHO information. No deaths from bird flu have been reported in the US; people who've tested positive for the virus historically have had direct contact with sick animals and exhibited mild symptoms.
In Canada, a teenager has been hospitalized with bird flu.
Is there a vaccine for bird flu?
There's not a bird flu vaccine available or recommended to people right now. However, the US has been investing in the development of vaccines that could be used in an emergency situation, should one occur. In October, the Administration for Strategic Preparedness and Response awarded about $72 million to CSL Seqirus, Sanofi and GSK to fill and finish additional doses of vaccines that could be used for avian influenza.
The US Department of Health and Human Services announced in early July that the government is providing Moderna with $176 million to develop its influenza mRNA vaccine, which could be used if bird flu starts spreading person-to-person or becomes a pandemic.
Can I get bird flu from milk, eggs or meat?
There haven't been any reports of people getting bird flu in the US from drinking milk or eating meat from birds or cows. The commercial food supply, which makes up most food you'd get in a regular grocery store, is regulated, and meat from impacted animals shouldn't make it to store shelves.
There have been fragments of inactive bird flu virus found in pasteurized milk samples since the virus started spreading to cows. The high-temperature pasteurization process inactivates any virus or bacteria, including bird flu, that could make people sick. Infectious virus has been found in raw milk, and the US Food and Drug Administration is reiterating the general health risks of drinking raw milk, not just in terms of bird flu but also for other pathogens that often live in unpasteurized milk.
In terms of meat, cooking ground hamburger is also expected to kill the bird flu virus, according to the Department of Agriculture. The same is true for poultry; according to the CDC, cooking eggs and poultry to an internal temperature of 165 degrees Fahrenheit kills viruses, including bird flu.
It might be difficult to catch influenza from food or drink anyway, according to infectious disease experts we've spoken to in the past since influenza (including bird flu) is a respiratory virus.
If you work directly with animals or livestock, which would include working on a farm, or even if you visit a fair where there's livestock, you should check out the CDC's specific tips for safety to reduce the risk of spread.