Coronavirus and cavemen

It seems only a few years ago that, when I walked around my house, the lights wouldn’t turn on automatically! For younger readers, I should explain that in the past you actually had to go to a particular place on the wall and press a switch if you wanted to be able to see things!

Can you imagine the inconvenience if, say, you had your hands full at the time? And when you left the room, if you wanted to save power, you’d have to do the same thing again, and then repeat it as you went into the next room. So people had to install switches in all the places they thought they might go in and out of rooms. They had to come up with complex wiring schemes because you might want to turn lights on at the bottom of a staircase and turn them off at the top, when the upstairs and downstairs lights were normally on different electrical circuits!

It’s hard to believe, in this era of easy home automation, that there are some people still living this caveman-like existence, but it’s true, just as there are those who, when they want to listen to the news, turn a physical dial instead of just talking to their smart speaker! Those whose house doesn’t know when they’re in movie-watching mode, so they have to turn the TV on and off with a remote control.

This is, of course, terribly inconvenient for those people who still embrace the ‘retro’ approach to life, but now it has an extra drawback: every one of those switches, buttons, knobs is a hot-spot for potential virus transmission. How are those people meant to protect their family from infection if, carrying in groceries or deliveries from the outside world, they have to press a light switch that everybody else in the family is going to touch later that day? And if, without thinking, they draw the curtains by hand, how many hands will touch the same spot later?

And that’s just home automation. When the lockdown is lifted, just imagine those poor people who have to go back to work in non-automated workplaces! The potential for contagion is terrifying.

But yes, my young friends, that’s what the world really used to be like for most people! Amazing, but true.

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I remain very unconvinced about the surface vector for covid-19 – Firstly, the R0 is way too low for that to be a significant fraction of the risk – it seems breathing air someone just coughed in is likely to dominate to transmission. Lab experiments (reported on Cambridge slack channel on surface survival) take nebulised virus and spread it on different materials and measure the half life of the surface load, for different materials – all very reproducible. but tells us zero about how likely someone is to being infected by touching an infected surface (who doesn’t then wash their hands before the next time they touch their face AND is not wearing a mask)….so the lab experiemnts aren’t even half the work.

Secondly, a lot of countries post lockdown use contact tracing, which mostly assumes human-to-human transmission not human-to-surface-to-human transmission (which would require you to know precisely where infected people had been, as well whom they’d been near) i.e. no actual contemporaneous co-location needed, so harder to tell.

So going the other direction, what fraction of people infected appear not to have been in contact with another infected person? that would give a rough idea of the proportion of this or related vectors’ contribution to the spread…

not that getting rid of light switches isn’t a laudable goal – for me, it is more about the aesthetic of not messing up nice walls!

Hope your Easter break has gone well!!!

Yes, agreed with all of the above – I wasn’t too serious and I imagine any risk is tiny compared to being in a confined space with infected people, or being downwind in an open space.

My brother, who works in public health, told me early on that surfaces were likely to be contaminated at the very worst for 72 hours, and that was if somebody known to be contagious had coughed fairly deliberately on it! So I’ve always assumed that anything coming to me by courier, once you’ve dealt with the outer packaging, is pretty certain to be safe just because it’ll have been in transit with no human contact for a day or two.

In the workplace, surfaces might be more of an issue, but the real challenge there, I imagine, is with door handles, and door-automation is a much more expensive and problematic than automating most other things. (Otherwise I would have done it by now 🙂 )

Your key point, though, about not knowing how likely it is that a human will be infected even from a known contaminated surface, is a good one. I too have wondered about whether subtraction is the only effective way to determine this…

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