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Al Haddrell Profile picture
@ukhadds
Jun 22, 2023 • 3 tweets • 1 min read • Read on X
I’m proud to have our latest research published on how long #SARSCoV2 remains infectious while airborne! We studied the fundamental processes that drive the loss of viral infectivity in the aerosol phase. #COVIDisAirborne

Here’s a thread going over some of the findings. Image
@ParentMishmash Interesting question btw. Actually, all of your questions have been. Thanks!
@J__Doh Here are the specific values. So, about 10 to 20 times faster decay in sunlight (depending on the season). Image

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More from @ukhadds

Al Haddrell Profile picture
Feb 2
This study made some waves on social media yesterday. It purports to show that CO2 concentration doesn’t correlate with covid transmission.

Let’s talk about this, I have some thoughts.

sciencedirect.com/science/articl…
Context: Why do people think knowing the CO2 concentration is important when it comes to Covid transmission?

There are 3 unique reasons.
1) Both CO2 and respiratory (virus containing) aerosol are exhaled. They are, to some degree, correlated. Meaning that if the CO2 concentration in a room is high, the amount of exhaled aerosol in the room may also be high.

Read 28 tweets
Al Haddrell Profile picture
Jan 19
You have no idea. Ironically, I found out about this letter when I was on my way to a dinner to celebrate the end of a 5 year covid project I was on. This project resulted in 14 papers in high impact journals where we explored how SARS-CoV-2 is aerosolised through talking/singing
Needless to say, to find out right then that the government had produced this letter was bizarre and upsetting. Like, why are we doing all of this research if they are just going to ignore it?

When I shared the letter with others on the team, it got a little awkward....
I literally posted this right after I left (hence the tone...).
Read 4 tweets
Al Haddrell Profile picture
Dec 29, 2024
If you got a CO2 monitor for Christmas and are wondering what exactly the device is used for, I’ve put together a video to walk you through some ways you can use it improve your indoor air quality, and to lower your risk of catching airborne viruses (C19)
With New Years coming up, you may be having friends over. You can use a CO2 monitor to see how best to ventilate your home, to make sure that your friends and family start the year off healthy! I walk you through how to measure your home's ventilation here
And of course, if you are having people around (along with good ventilation) you ought to also consider masking.

In this video I walk through how masks work to remove infectious aerosol from the air that you are inhaling. Hint: they work like your lungs!
Read 4 tweets
Al Haddrell Profile picture
Dec 28, 2024
I was asked to walk through why the work published earlier in the year by the Lund group is so important. I’ve put together a thread to walk through some of my thoughts.
First, here’s a link to the study.
nature.com/articles/s4159…
Let’s start with some context. Airborne viral transmission is exceedingly complex, but can be broken down into 3 general processes: production, transport and exposure. To estimate transmission and to design effective mitigation strategies, you must understand these processes. Image
Read 22 tweets
Al Haddrell Profile picture
Dec 8, 2024
Thanks for your interest in our work. You’ve asked a lot of “out of the box” questions here, and I’ll address some of them.
Exhaled aerosol has a water activity of ~0.995. The RHof fog could be higher: the the aerosol would simply take up water from the gas phase. For viruses such as influenza, where the salt concentration seems to be very important, this would lead to an reduction in the decay rate. Image
This is a good question that we need to explore. Understanding airborne microbe decay is highly dependent on understanding the aerosol dynamics. And the pH dynamics in an aerosol is very complicated and need of a lot of study. Image
Read 11 tweets
Al Haddrell Profile picture
Nov 1, 2024
A study came out last month looking at how long influenza remains viable in the air.

In the article, it highlights some of my larger concerns in what is happening in the field of airborne viral decay.

First off, here’s the article:

frontiersin.org/journals/micro…
Out of the gate, the article is fine.

My largest critique is the assertion that 99% decay means something. Why 99%? Why not 98%? Or 97… or 92… 87%? 83.5%?
While it sounds like I’m being coy, I’m not. 99% is an arbitrary number. That’s okay, but don’t act like it’s an agreed upon value. It isn’t.

Anyway, this is a minor issue (of someone in the field). The general trends presented by the authors is supported by their work. Image
Read 16 tweets

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