H5N1 – The Scale of the Threat

News this Week

This week marked a very concerning development in H5N1. A teenager in British Colombia is the first known case of H5N1 in Canada. It’s an odd coincidence that the province is adjacent to the first US state to have had a confirmed COVID case in 2020.

There are two things about this that are the most alarming. First, the teen didn’t have any underlying medical conditions. “The teen first went to the emergency department on Nov. 2 and was tested and sent home, but returned to hospital days later when symptoms worsened” and is now in critical condition. We don’t have any details other than presumptive pneumonia, but to me that suggests that they developed acute respiratory distress syndrome (ARDS) induced by a cytokine storm.

ARDS is a serious lung condition that occurs when fluid builds up in the tiny air sacs (alveoli) in the lungs, leading to critically low oxygen levels in the blood. This condition can develop rapidly and is often associated with severe illnesses or injuries, such as sepsis, pneumonia, COVID-19, or trauma.

This is what was happening with the Spanish Flu in 1918. “British military doctors conducting autopsies on soldiers killed by this second wave of the Spanish flu described the heavy damage to the lungs as akin to the effects of chemical warfare.”

There hasn’t been an update on the teen recently, which I suspect may mean no improvement.

The second alarming thing is the results of the sequencing of the virus from the teen. One thing about H5N1 so far has been that the virus has not been easily spread person to person. However, the virus from the teen had two key changes in the hemagglutinin gene. Hemagglutinin is a protein on the surface of certain viruses, including influenza, that binds to the sialic acid receptors on cells that it will infect. Think of it as the key that unlocks the door to gain entry into the cell. Those two substitutions are known to enhance binding to mammalian receptors, ie, it makes it much more easy to infect a person.

Why this Is Important

I tweeted this almost two years ago.

We are getting very close to human-to-human transmission. That risk will increase significantly as seasonal influenza comes into play. Influenza is a very sloppy replicator and will mix its genes as well as mop up genes from the environment.

People simply do not comprehend the scale of what could happen with H5N1.

Even if we took a more conservative mortality rate of 25%, that still means 600 million deaths worldwide. For another perspective on that number, it would be like everyone in the United States (except those in Massachusetts) dying…TWICE.

Those number also are assuming that everyone infected would get good healthcare. We don’t have that capacity, so the numbers would likely be much higher.

In addition, it also doesn’t reflect the mortality related to other causes as supply chains and services are disrupted.

There is another wild card today that didn’t exist in 1918 – immunocompromised people. If cytokine storms are the result of a healthy, overactive immune system, what happens at the other end of that spectrum among those with untreated HIV or are on immunosuppressants? Does that mean that they could amplify the virus and become superspreaders? I tweeted about this as well.

The COVID pandemic should have alerted us to how fragile supply chains are, but we continue to live in denial about that. Even domestic production is no panacea in the world of climate change. This was obvious due to the shortage of IV fluids as a result of the remainder of Hurricane Helene passing over North Carolina.

We live in a world of very complex systems. The more complex a system is, the more opportunities it has for failure. This problem was addressed very well in an article by Debora Mackenzie in the New Scientist in 2008. This is the one to read if you really want to have a grasp of this threat, but it is behind a paywall. I found the text of it here as well.

If you wonder how I sleep at night, lately, not very well.