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Ask HN: Do anti-C19 foggers do any good or is this performance?

28 points by ggm ↗ HN
Lots of imagery on TV shows handheld foggers misting public spaces. I am confident this stuff works for mosquito borne disease, all it has to do is stop hatching of larvae. It appears popular in Asia, south America, Africa, India. I am trying not to assume this is bogus populism.

But, do these mister units actually do anything useful against an aerosol dispersed disease? It feels from here behind the TV set its performative hygiene theatre, and does nothing of substance. Because of mosquito control they have the devices, and they can fog bleach, or TCE or something (that would be terrible)

Or, are "fomites" still a real concern?

UV was said to be used to "sterilise" aircraft interiors. I would probably ask the same question: does it do anything useful?

28 comments

[ 199 ms ] story [ 265 ms ] thread
voldacar
Fogging, wiping, etc is disease theater, much like the TSA is security theater. There has not been a single case of covid that has been definitively linked to a fomite.

Here is a review of some studies that mention cases linked to fomites: (scroll down)

https://ncceh.ca/documents/evidence-review/fomites-and-covid...

In each case, the link is pretty tenuous. Each of these events could be explained (much more parsimoniously, imo) by respiratory droplets in the air.

unbanned
However, SARS-CoV-2 RNA has been found on environmental surfaces in hospital rooms, quarantine rooms, and other community settings, implying that the surfaces can become contaminated with SARS-CoV-2 despite few studies being able to culture live viruses.46,52,79-82 Additionally, new variants with potentially greater transmissibility continue to emerge, and they may behave differently on surfaces than the strains that have been studied to date

So yes, there is a reason to do what you say is "theatre"

oxfordmale
Wearing masks and handwashing is much more effective than foggers.The scientific evidence for fogging’s effectiveness remains largely inconclusive and official bodies such as the Centres for Disease Control and World Health Organization do not recommend it as a primary method for combatting the spread of the coronavirus.
Beldin
Since when are viruses considered alive?

When i was taught biology, they weren't alive, but also not quite non-living. If memory serves, that is (it's been a while).

netizen-936824
I learned that they're kinda alive. With the ability to reproduce only using the machinery of living cells to replicate their genetic material and proteins

The world isn't necessarily black and white

elzbardico
I assume that when people say alive related to viruses in the environment, they mean viable
netizen-936824
Could you please cite the sources that state that viruses are viable on surfaces? I remember reading a study about surfaces in COVID patient rooms not being viable, but was unable to find this study quickly. I did find a different one though. This one states there is not enough evidence for viability.

https://www.ncbi.nlm.nih.gov/labs/pmc/articles/PMC8302502/#_...

ianai
We’ve known all along that coronavirus can remain intact on surfaces for days. There’s reason to believe omicron would last longer than others: https://www.news-medical.net/amp/news/20211208/Computational...
netizen-936824
That's a study on ACE2 binding affinity, not a study on surface viability....
ianai
“ Secondary structural analysis of the Omicron variant reveals a higher proportion of alpha-helices than the Delta variant but less extended strand and random coil structures, leading to more structural stability.” It goes on from there.

They found reasons to suspect the omicron variant is all around more resilient to the environment and more contagious. Thus the connection to fomite and aerosol concerns.

netizen-936824
First: that is an entirely computational study. Computational studies are a great starting point but must be confirmed with real world tests

Second: stability != surface viability. The study literally mentions nothing about the ability of the virus to survive on inanimate objects. Yes some proteins may be more stable in some cases, but we need to test the viability of actual virus particles taken from actual surfaces after varying residence times

Third: all real world evidence and meta-analyses have come to the conclusion of extremely limited to no viability from fomites

Fourth: the part of the study which mentions stability has the following gem:

>Regarding stability scores, the researchers discovered that the stability across all spike proteins ranged between 32.8 and 34.7, slightly below the value of 40 that indicates a protein is structurally unsound.

These proteins are not very stable to begin with, so marginal improvement over wildtype basically says nothing. Not to mention the article does not mention fomites anywhere at all. So you literally cannot draw that conclusion. That is what shitty popsci reporters do, which is the wrong way to interpret research. We just cannot make logical jumps like that when dealing with insanely complex systems which we don't fully understand.

It's going to take way more than a single, limited computational exploration of protein structural stability to convince me of fomite viability. I'm saying this as a formally trained biochemist

ianai
Sorry, I thought you were just yet another denier of anything/everything on the internet.
netizen-936824
In my opinion you have nothing to apologize for. My writing tone can come off as abrasive but that's not intentional, so I do apologize for that. There's tons of stuff I don't fully understand either, especially in the bio fields. Computers are complex, but biological systems are more complex by multiple orders of magnitude. Many of these things we don't yet have a full understanding of and the research methods to elucidate biochemical mechanisms are also complex.

It's also possible that I may be wrong about surface viability. I started out in the pandemic assuming the virus is viable on surfaces but after research has come out I have essentially stopped washing my hands altogether (outside of the normal times I did before).

This is difficult for everyone as we all can have varying levels of understanding and different perspectives. Yet we all have to deal with this in the best ways that we can figure out.

elzbardico
There have been no documented case of contagion from contaminated surfaces. This is the hard science, fogging based on what if is not, it is theater indeed.
netizen-936824
and most studies of surface viability conclude that there is minimal to no risk from surfaces

Its good to start out conservative in this regard where we assume viability everywhere, but evidence now points elsewhere

sto_hristo
Just because there is no documented case, that doesn't imply impossibility. Your hard science doesn't prove contaminated surfaces to be safe and until that happens, people with common sense make the correct assumption that such surfaces are a possible vector; just how it is with other viruses, germs, etc.

I will never forget how my company brought in a virologist from one of our best hospitals to explain to us this covid thing that is in the news - this back in Jan, 2020, about 50 minute live lecture. Throughout the talk she kept making it very clear that our country was completely covid free, that they have taken measures like temperature checking of incoming passengers. I guess that moron also thought that just because you don't see air, air doesn't exist. About a month later we were in total lockdown, people were pruning their work monitors to take them home... Funny.

netizen-936824
There is no significant risk of surface transmission

https://www.nature.com/articles/d41586-021-00251-4

rapjr9
If you actually read that article it says surface transmission is a _minor_ risk and is possible. It's not zero risk. It's also difficult to prove it is or is not happening. Omicron is thought to replicate faster, so a smaller amount of it could be a larger risk, including on surfaces. Has anyone studied Omicron surface viability specifically? At the very least, if someone wipes their nose with their hand, then touches a door handle and then another person soon after touches the door handle and then wipes their nose with their hand that is a lot like taking a swab from one person and putting it in the nose of another. So surface transmission seems obviously possible (and there are a couple known possible examples of it in the article), but doesn't seem to happen as often as aerosol transmission, but it is also hard to measure in the wild so it is still something of an unknown. Lots of people have stopped washing groceries and are doing ok. Lots of people still are using Purell very often also. Keeping the virus off your hands so you don't introduce it to your mouth or nose seems like a good idea. Trying to sanitize objects is recommended in the article, but only after other countermeasures and only if you have the time. Sanitizing your hands accomplishes the same thing as sanitizing surfaces -if- you always remember to sanitize your hands before touching your nose or mouth after touching something that might be contaminated. Viruses degrade with time on surfaces at varying rates, so infectiousness drops with time. The article says we don't actually know what that decay over time is in the wild. It also says there have been no conclusive cases of surface transmission, but that's only because it is hard to observe in the wild. How do you tell if someone breathed it or touched it? So "no evidence" here means "we don't know and can't figure out how to do a good experiment since we can't intentionally infect people". Aerosols are definitely the higher risk, but you can't rule out some surface transmission. Risk likely varies by surface location as well. A ceiling is low risk, opening your car trunk is probably low risk, a public bathroom door handle is higher risk.
voldacar
Your comment is just not scientific

We have known that the virus can exist temporarily on surfaces since the beginning of the pandemic. Over countless millions of cases, there is still no evidence that anyone has ever been infected by contact with sars-cov-2 viruses on a surface.

> they may behave differently on surfaces than the strains that have been studied to date

"may" is doing the heavy lifting here. My priors for a small number of mutations being able to change the way a virus behaves on a surface are exactly equal to zero.

unbanned
My comment is a quote from the journal so...
ianai
Delta was already transmitting similarly to or faster than measles. Omicron vastly outcompetes delta. A quick search for measles and fomites shows its surface half life is 2 hours and a wide concern for fomites.
traceroute66
My guess would be that the idea behind fogging is to weigh down aerosol in the room. It has been well documented by scientists across the internet that COVID aerosols could remain in a poorly-ventilated room for a number of hours, this is because scientific thinking from reputable sources has now moved from "aerosolised droplets" to "airborne" (hence the importance of high-quality masks and not some random piece of cloth cut off an old t-shirt).

So it could be therefore argued that in the absence of other (more preferred) options, fogging is a decent last resort to try to combat stagnant COVID aerosol because it will weigh down and/or disperse and/or dilute stagnant areas of COVID.

Of course it is well understood by now that the preferred means to combat COVID is high levels of ventilation (open windows) and filtration (HEPA filters). But this is not always possible to achieve in an ideal manner either due to building construction (sealed windows etc.) or climate (cold weather, windy days etc.). So it is quite possible that using fogging as a "plan B" should not be entirely disregarded.

(Disclaimer: I am not a scientist, the above is a simplified summary of my understanding based on what I've read from reputable scientists)

rightbyte
In theory saturating room moisture should make droplets fall out quicker. However it seems way easier to just install fans than to have fog machines. Imagine the mould problems.
VoodooJuJu
I'm sure they do plenty of good for the wallets of the people selling these things.
nikolay
Bulgaria had aerial theaters - a few mayors decided to step up a notch and sprayed their whole villages and their vicinities with disinfectants.