Hopefully Interesting

A little while ago I finished reading Plagues Upon the Earth: Disease and the Course of Human History .  It was a a very good book about exactly what it says on the tin.  There was a bunch of fascinating science in it but one part clarified some ideas I'd had noodling around in my head prompted by Covid and I'm going to outline those bits here. Back in prehistory there were very few epidemic diseases spread from human to human.  In a band of 100 people a disease like influenza will rip through everyone in short order.  But afterwards, everybody's immunity will be at a peak and that disease lineage would die out.  This isn't to say that humans would never get the flu, just that each outbreak would be the result of a new zoonosis or crossover from animals to humans.  Other diseases like Cholera exist harmlessly in the environment most of the time, attaching to the shells of crabs, until some human happens to drink it in and then it expands out of control wit...

It's been a while since the last two posts on the topic so it seemed like a good idea to write down what I'd learned or changed my mind about recently on the topic. Immunity changes symptom timing One thing that's become important in the Omicron wave is that it seems that if you train your immune system to recognize a disease then you'll develop symptoms of that disease more quickly than if your body doesn't recognize it.  Most of the symptoms we tend to get when sick like inflammation or a fever aren't directly caused by the disease but by our body's innate immune system fighting it.  I'm actually not sure exactly why adaptive immunity leads to triggering innate immune responses faster but it's apparently a thing.  Michael Mina has a nice infographic here on the topic which is also arguing that this means waiting 5 days after symptom onset to return to work might now not be good enough when previously it would have been. Previously the one genuine...

 New sooner have I posted about the Coronavirus then a couple of new things come up. Yesterday I came across a really great paper,  Beyond Six Feet: A Guideline to Limit Indoor Airborne Transmission of COVID-19 .  It's related to a tool for figuring out risks of indoor aerosol transmission but the information in that paper was what was really interesting to me.  I'd thought that aerosols were only generated by our lungs' alveoli but apparently they can be generated by vocal cords too when you use them to speak, sing, etc.  I suppose the bit I had read earlier was making the simplifying assumption that people are silently sitting still or something.  Anyways, I'd been really interested in how much of what size of aerosol or droplet was generated by what sort of vocalization and what should this paper have but the graph I'd always wanted.     I'd previously been told that 2.5 micron aerosols are most common which looks to be  approximatel...

I've fallen a bit out of the habit of blogging so I figured I'd do something fairly easy to start to get back in the habit.  Over the course of the pandemic I've been learning a lot about virology.  Most of this is, as far as I can tell, very basic stuff from the perspective of a virologist but it was surprising to me and might also be new to you who are reading this. Viral Load First of all, viral load is important.  I'd normally thought of people as either sick with a virus or not sick previously.  The easiest way to look at this is from the tools we use to detect viruses.  The way a PCR machine works is that you double the amount of viral RNA in a sample again and again and eventually you have enough virus to detect it by macroscopic means.  The number of times you have to double the amount of RNA before it becomes detectable is called the cyclic threshold or CT value.  For a sensitive PCR machine you can detect RNA down to a CT of 37 to 40.  A...