I've been asked - especially after public talks / twitter threads on aerosol disease spread - how I personally behave. A few things to bear in mind. 🧵 First - my background can tell you *relative* risks. That doubling ventilation or HEPA can halve your risk, and wearing FFP2 reduce it at least ten-fold, compared to without. But these don't tell you *absolute* risks... 2/

There have been a number of articles claiming recent findings from UEA show air filtration does not reduce the spread of Covid. But the pre-print shows the opposite


1/mcknights.com/news/clinical-…
independent.ie/irish-news/cos…
uea.ac.uk/about/news/art…
medrxiv.org/content/10.110… They did a systematic review of a number of different technologies at stopping a range of diseases. They found some were more effective than others. HEPA filtration, for example, consistently showed a 30% reduction in people with symptoms! So how does that give "ineffective"? 2/

Seasonal winter viruses driven by drier indoor air in winter. Why is it drier in winter, why does that make viruses spread more easily, and what can we do with that info? 🧵on article 👇 1/ annualreviews.org/doi/pdf/10.114… "Isn't it driven by us spending more time indoors together when the weather's worse?" Probably not - in industrialised world, we spend most of our time together indoors anyway. So it's indoors that counts. 2/

Thread: How do we make the air in classrooms safer?
All you need to know about HEPA filters,CO2 monitors and ventilation. Contents: basic ideas; how to with links to resources; caveats; links to studies / evidence (that I'll add to cos takes more time) 1/ Airborne respiratory diseases (TB, Covid etc) are all transmitted the same way: pathogen is in tiny particles that we breathe out / give off when speaking. They're small enough to stay in the air like smoke; you get more if you’re closer but eventually the whole room is smoky 2/

Really interesting findings. tl;dr: rigourous study confirming that infectious COVID virus is found in the aerosol particles down to the tinest ones (<1 micron) that are given off in breathing and speaking, and can stay in the air for hours. Even more tl;dr: definitely airborne.

https://twitter.com/linseymarr/status/1428083885527736320

Previous studies have found viral RNA in aerosol particles that float in the air - but skeptics have suggested this is "dead" RNA. Other studies have tried and failed to grow actual COVID from these air-extracted samples - but that's just cos their experiments didn't work... 2/

Very good thread. Those opposed to "zero covid" need to clarify what they're suggesting instead. At the end of the day, either R<1 or R>1.

https://twitter.com/yaneerbaryam/status/1365497804601360387

Keeping R<1 will become easier and easier with vaccination. Under these conditions, covid levels die away, and flare-ups can be stamped out.

The new COVID variant and how we should behave to be safe. tl;dr: it hasn't acquired resistance to anything; soap, distancing, masks and fresh air all still work; but we should act like people indoors are giving off more than they were. First the science: the new variant is surrounded by the same lipid coating so still killed by washing hands with warm water + soap. Infection still carried in the same tiny droplets given off when breathing / talking; fresh air / masks / distance still reduce this transmission.

COVID can be airborne, in floating “aerosol” particles. We know how these particles move, and how long they stay in the air. What does this mean for minimising risk? TL;DR: ventilate rooms to stop aerosol levels building up; masks and distancing still help but 2m not magic bullet Aerosol particles are given off especially when someone is talking, without a mask, like a smoker giving off smoke.

https://twitter.com/MWStory/status/1309561305616076800?s=20

If that person has COVID, and someone else breathes in their aerosol, that can pass on COVID infection.