- H5N1 is a form of bird flu that is raising concerns among health officials
- The virus has been around for 25 years and rarely spreads to human
- Still, recent reports of outbreaks in other mammals have officials monitoring the situation closely
Since the World Health Organization (WHO) declared COVID-19 a pandemic on March 11, 2020, other viruses have also circulated in large numbers.
In 2022, California and New York declared states of emergency in response to monkeypox, a viral infection with hallmark lesions. And a “tripledemic” of illnesses (COVID, flu, and RSV) alarmed experts this winter.
People may be sick of being — and hearing — about sickness. But experts are now concerned about another virus, H5N1 influenza, also known as the bird flu.
At a virtual briefing on Wednesday, February 8, WHO officials stressed that the risk to humans was low but needed to be monitored closely.
Still, the spread of H5N1 — a virus commonly affecting poultry and birds — is raising flags and questions, including whether bird flu could start another pandemic.
Below are answers from health experts to some of the most common questions people have about bird flu, the potential dangers, and how you can best protect yourself.
What is bird flu?
As the name implies, bird flu is another variant of the influenza virus that commonly infects birds.
“The flu virus is able to infect multiple species so not just humans, but birds and other mammals,” says Sharon Nachman, the chief of the division of pediatric infectious diseases at Stony Brook Children’s Hospital. “Each time it infects another species, there is a chance for it to change some of its outer proteins, making protective antibodies from a prior infection worthless.”
The current concerns are around a strain of the bird flu known as H5N1. According to the CDC, the first case of H5N1 was detected in a domestic waterfowl in 1996 in Southern China.
“H5N1 is named because of the surface proteins present on the virus and is one type of Avian flu,” says Jason Zucker, MD, an infectious disease specialist at NewYork-Presbyterian/Columbia University Irving Medical Center.
Can Bird Flu spread to humans?
Yes, Nachman says the bird flu can spread to mammals, including humans. Between 1996-97, 860 people were infected with the virus, with outbreaks occurring in China and Hong Kong.
Yet, you may have never heard of this virus. There’s a reason for that.
“Bird Flu rarely spreads to humans,” says Zucker. “When it does, it mostly occurs through close contact with an infected animal. While human-to-human transmission is reported, it is rare and most frequently occurs with people living in the same household.”
Zucker says that Infection spreads from an animal, usually a bird, to a human through:
- nasal secretions
What are the symptoms of bird flu in humans?
“Reported symptoms look similar to the common flu, and just like with the flu, we know range from mild illness…to more severe illness,” Zucker says.
Common symptoms of bird flu might include:
- sore throat
- muscle aches
- trouble breathing
Why is bird flu spreading at such high rates among animals recently?
Experts say it’s unclear.
“[When H5N1 was first discovreed], scientists were worried that it would cause an influenza pandemic,” says Jay Varma, MD, Kroll’s chief medical advisor, a Kroll Institute Fellow, and the director of the Weil Cornell Center for Pandemic Prevention and Response. “Since then, it has primarily circulated among birds and occasionally infected mammals — everything from tigers to foxes to seal — and a relatively small number of humans.”
But a recent report noted an outbreak of H5N1 in farmed minks in Spain in October. A preprint that hasn’t been peer-reviewed reported a potential outbreak in the summer of 2021 in seals in New England.
What’s different now?
“Scientists believe it primarily spreads to different areas of the world and different animals when birds fly long distances and come into contact with other animals or the birds are eaten by animals,” Varma says. “But they still do not understand all the factors, from the virus itself to environmental conditions, that determine how this virus spreads.”
How deadly is bird flu in humans?
That’s something experts are watching closely but still don’t know. According to the CDC, the H5N1 outbreak in 1996-97 had a more than 50% death rate. But that doesn’t mean the virus will have the same effect more than two decades later.
“It’s too soon to say how deadly any specific variant of influenza virus will be,” Nachman says. “Usually, this virus has seasons when it drifts serotypes and rarer seasons when it shifts serotypes. A drift means there is a small change from year to year, so if you had the flu last year, you are less likely to get very sick when you see the drifted variant this year.”
The caveat: “If it’s a shifted virus, then it is less likely that you have any antibodies that will help to protect you, and therefore, you will be more likely to be sick,” Nachman says.
In other words, officials are still unsure.
Is bird flu seasonal like the regular flu? If so, should we be optimistic heading into spring?
You may have been hoping we were at the tail end of “sick season.” Now, word of bird flu is concerning. Nachman delivered an all-to-familiar refrain in response to questions about bird flu’s seasonality.
“It’s a question of wait and see what circulates and then follow the science,” Nachman says.
Varma concurs, adding, “Because there are northern and southern hemispheres that experience opposite seasons, there is always an opportunity for avian influenza to be circulating somewhere in the world.”
Why are experts raising concerns about Bird Flu now?
Zucker notes that there has not been a confirmed case of bird flu in humans in 2023. But outbreaks in minks and potentially other animals like seals marked the first large ones of H5N1 “driven by mammal-to-mammal transmission,” according to a JAMA report published on Monday. Authors noted, “renewed concerns that H5N1…could be poised for spillover into humans.”
“This is a large outbreak, affecting multiple species, and we are seeing confirmed mammal-to-mammal transmission in animals like mink, which puts it close to humans,” Zucker explains.
Could bird flu cause another worldwide pandemic?
That’s the fear. Is it possible? Maybe, but it’s still too soon to tell.
“This will require careful surveillance, and we do not know if or how this will affect humans, but it is important to stay vigilant,” Zucker says.
Is there anything people can do to reduce the dangers of bird flu to people or animals?
To lower the risk that you or an animal catches bird flu, the CDC recommends:
- avoiding direct contact with wild animals, including ones who appear ill or sick
- policies on handling dead birds vary by state and locality. If you are told by local officials to put a carcass in the trash, put on gloves or a plastic bag turned inside out
- get a seasonal flu shot
“And, as always, good hand hygiene is important,” says Zucker.
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