First bird flu death in US confirmed.

No change in threat assessment. But a warning shot, nonetheless.

Getty Images/Kateryna Kon/Science Photo Library

Officials in Louisiana confirmed the first death of a US resident due to H5N1 bird flu. The case, affecting a man older than age 65 with underlying medical problems, was announced last month. At the time, the case was described as “severe,” implying dangerous respiratory disease or other organ failure.

The Louisiana case was caused by the D1.1 variant of H5N1, which caused a severe case in an apparently otherwise fairly healthy teen in Canada. The child nearly died but is doing better now (though her mental and overall physical status are not public, we do know she no longer requires life support or other intensive care). There were a few cases of D1.1 in the US in Washington state in 2024, though to my knowledge, none required hospital care.

The D1.1 variant is associated with birds while another variant, B3.13, caused dozens (and perhaps hundreds) of mild illnesses in dairy cattle workers in the US in 2024.

In December, California declared a state of emergency regarding H5N1, primarily due to high levels of virus in animals there, as well as detection of the virus in commercial products like raw milk.

Now what?

While concerning, the death of the Louisiana man does not change my threat assessment for H5N1. (Here’s what I wrote about this all last week in Inside Medicine and in Slate.)

Here are three things that would raise the threat level, warranting more public concern.

1. Evidence of human-to-human transmission. Even without an uptick in severity, that would mean that H5N1 could infect many people in a short period, which would raise the chance of coinfection with seasonal flu. This is how flu pandemics are born (see the previous pieces above).

2. Evidence that larger numbers of people are getting infected outside of high-risk settings such as dairy farms where the virus has taken hold. How many? Tough to say.

3. Evidence that the B3.13 causes severe disease. The B3.13 variant is the one that has caused the greatest number of infections in US residents during the 2024-2025 outbreak, mostly in farm workers. Fortunately, no serious cases have occurred. That could be because the farm workers were “too healthy” to become severely ill from the virus. So, if working-age adults (let alone older or other at-risk people) getting B3.13 suddenly began getting sick enough to warrant hospital-level care, that would raise my concern.

What to watch for. (Mostly it’s risks, not symptoms.)

The main symptom that has stood out in mild cases of H5N1 is conjunctivitis (redness of the eyes). In the recent New England Journal of Medicine report, 93% of the 45 described patients had conjunctivitis. That said, eye redness is a conspicuous and somewhat unusual finding for flu, so that alone may have prompted seeking medical care. Meanwhile, people without that outwardly unusual symptom may not have sought care or a diagnosis. So, the 93% figure may be an overestimate of reality. Still, it’s the main symptom I’d watch for. By comparison, fever (or feeling feverish) was only found in around half of the patients.

The big thing isn’t any symptom, but exposure risks. So, anyone who has a respiratory or flu-like illness and works on a dairy or poultry farm (especially in states with known outbreaks in those animals; right now, California is the real problem area), carries increased risk. Other risks include exposure to products like raw milk, or handling dead or sick birds in any context.

A dangerous time.

January is a bad time for all of this. If someone has bird flu, it may fly under the radar, as millions of Americans are also coming down with seasonal flu, Covid, and RSV right now. That means that barring an unusual presentation of symptoms, detecting bird flu might be tough—akin to finding a needle in the haystack.

What I’m doing.

As you know, I wear a mask at the hospital during every patient encounter. I also mask in some high-density settings. While I do this intermittently, this is harm reduction. The fewer chances we give viruses to infect us, the better off we are. January is absolutely my peak month for mask-wearing and especially rigorous hand hygiene.

And I’ll say it again. While the seasonal flu shot is not likely to provide protection against bird flu, it will lower your risk of infection temporarily, which would lower the risk of a dangerous coinfection of seasonal flu (which is common right now) and bird flu (which remains rare). So, now would be a great time for a seasonal flu shot, if you haven’t gotten yours yet.

The vaccine works within a week or two. Who knows, you could even prevent a pandemic.

We’ll continue to follow this story…

Stay safe everyone!

—Jeremy