Thread by @maolesen

1-8

I thought I would explain why I am so concerned about H5N1. Even if it isn't causing severe illness and death at present in humans, each infection exponentially increases the chance of mutation to a version that would.

2- To date, the case fatality rate has been about 56%, although that number could be high due to insufficient testing leading to case ascertainment bias.

cdn.who.int/media/docs/def…

3- Here's why I said exponential. Each cell that gets infected can produce about 10,000 - 1,000,000 additional copies of the virus.

cell.com/biophysj/fullt…

4- Thousands of cells are infected in a person, so the infected person is producing trillions of new virus copies regularly until the infection subsides.

5- In addition, influenza is a very sloppy replicator and mutates regularly, hence the need for a new booster each year. It's also known as a promiscuous virus in that it picks up genetic material from its environment and can incorporate it into its genome.

6- Some of the replication is so bad that it produces non-viable virus copies. The other end of that spectrum is true too though, in that it can produce a more transmissible and more lethal virus.

7- That's where evolution kicks in. A virus can't succeed if it kills too many people too quickly because it burns out its potential hosts. That's what makes COVID such a perfect virus. It mutates and causes reinfections, but also VERY slow deaths that will take 1-2 decades.

8-8 A H5N1 pandemic could easily do just the opposite with high mortality and rapid spread, wiping out a billion people in a year. I really hope that doesn't happen but this is the kind of thing that makes me lose sleep at night.