CDC Statement: First H5 Bird Flu Death Reported in United States

Photo Credit - CDC

#18,532

Shortly after last night's announcement from the Louisiana Department of Health the CDC posted the following statement on the first H5-related death in the country. 

While it it doesn't provide much in the way of new information, it does remind the public that the relatively mild presentation of HPAI H5 in North American patients isn't typical of what we've seen with H5 viruses in the past. 

This fatal case - and the severe case in a teenager in British Columbia - are both linked to the new D1.1 genotype, which arrived in migratory birds this fall.  The majority of `mild' cases in 2024 have been caused by the `bovine' B3.13 genotype. 

First the CDC Statement, then I'll return with a postscript.

First H5 Bird Flu Death Reported in United States

Statement
For immediate release: January 6, 2025
CDC Media Relations
(404) 639-3286
https://www.cdc.gov/media/

January 6, 2025 -- CDC is saddened by Louisiana's report that a person previously hospitalized with severe avian influenza A(H5N1) illness ("H5N1 bird flu") has passed away. While tragic, a death from H5N1 bird flu in the United States is not unexpected because of the known potential for infection with these viruses to cause severe illness and death.

 As of January 6, 2025, there have been 66 confirmed human cases of H5N1 bird flu in the United States since 2024 and 67 since 2022. This is the first person in the United States who has died as a result of an H5 infection. Outside the United States, more than 950 cases of H5N1 bird flu have been reported to the World Health Organization; about half of those have resulted in death.

CDC has carefully studied the available information about the person who died in Louisiana and continues to assess that the risk to the general public remains low. Most importantly, no person-to-person transmission spread has been identified. As with the case in Louisiana, most H5 bird flu infections are related to animal-to-human exposures. Additionally, there are no concerning virologic changes actively spreading in wild birds, poultry, or cows that would raise the risk to human health. (CDC reported previously on its analysis of the viruses isolated from the patient in Louisiana.) However, people with job-related or recreational exposures to infected birds or other animals are at greater risk of infection. For these and others, CDC has developed prevention resources about how to protect yourself.

CDC is continually:

• Supporting critical epidemiologic investigations with state and local partners to assess the public health impact of each H5 case.
• Working closely with state and local partners to conduct active surveillance for H5 cases.
• Monitoring for changes that might suggest H5 viruses are becoming better adapted to mammals and therefore might spread more easily from animals-to-humans or human-to-human or cause more severe disease.
• Monitoring for any viral changes that could make these viruses less responsive to flu antiviral medications or the available candidate vaccine viruses.

Additional information about H5 bird flu is available on the CDC website.

We've known for a long time that closely related H5 strains can produce vastly different virulence and/or transmissibility.  

Some of those differences may be due to the local availability of medical care, host differences (age, vaccination and previous influenza exposures, preexisting conditions, etc.), and even the quality of surveillance and reporting. 

But notably, over the past 20 years:

• At the same time that Indonesia was reporting an 84% fatality rate (158 out of 200), Egypt was reporting a slightly less horrendous 33% (120 out of 359).

• Countries like Bangladesh, reported an even lower CFR (1 out of 8). 

• Since early 2023 Cambodia has reported 18 human H5N1 infections (clade 2.3.2.1c), with nearly a 40% fatality rate. And as we've seen previously with other incarnations of HPAI H5N1, Children and adolescents have been the hardest hit.

As a segmented virus with 8 largely interchangeable parts, the flu virus is like a viral LEGO (TM) set which allows for the creation of new subtypes - and within each subtype - variants called genotypes.  

There have already been more than 100 H5 genotypes identified in North America since the virus arrived in late 2021. Globally, that number is much higher. 

Most of these genotypes will fail to thrive, or be unable to compete with more `biologically fit' viruses.  Genotype D1.1 could end up as a brief flash in the pan, or it could become the new dominant strain. 

All of which means it is difficult to predict what kind of H5 virus we may be dealing with 3 or 6 months from now.  It could be a mild, attenuated virus or it could be something considerably more daunting. 

About the only thing we can assume is the virus - which has access to a growing number of susceptible avian and mammalian hosts - will continue to evolve.  

And we need to be prepared for more surprises along the way.