Considering you’re exposed to water during limited times (and need to actually ingest it) but exposed to air 24/7 (or else you die) that doesn’t seem like a reasonable comparison.
If someone standing in front of you sneezes, a filter in the HVAC isn’t doing anything to stop you from getting covid.
I mean, isn’t airborne transmission still uncertain for Covid?
We don't have to eliminate all transmission to stop Covid, we just need to bring the R value below 1 and keep it there. I don't think that direct transmission via sneezing is a significant cause of spread, but sneezed particles could remain in the air for a long time, long enough for a filter to make a difference.
>Recent investigations into the March 2003 outbreak of SARS in Hong Kong have concluded that environmental factors played an important role in the transmission of the disease. These studies have focused on a particular outbreak event, the rapid spread of SARS throughout Amoy Gardens, a large, private apartment complex. They have demonstrated that, unlike a typical viral outbreak that is spread through person-to-person contact, the SARS virus in this case was spread primarily through the air. High concentrations of viral aerosols in building plumbing were drawn into apartment bathrooms through floor drains. The initial exposures occurred in these bathrooms. The virus-laden air was then transported by prevailing winds to adjacent buildings at Amoy Gardens, where additional exposures occurred. This article reviews the results of the investigations and provides recommendations for maintenance and other measures that building owners can take to help prevent environmental transmission of SARS and other flulike viruses in their buildings.
I assume those floor drains lacked a functional p-trap because I've read with covid that disease would spread through drains without a proper p-trap, but otherwise the p-trap prevents drains like toilets and sinks from stinking and allowing contaminated air through.
P-traps can dry out though, but they stink if they do. Maybe that's what happened there?
Edit: yes, that's the theory - floor drains with dry u-bends allowed the poop air out.
It also had a cracked vent pipe. Sickness was correlated with floor level (the higher the floor level, the higher the infection rate).
The important takeaway is SARS 1 had significant fecal-oral transmission and not just respiratory.
And yet I'm supposed to believe that SARS 2 is respiratory only despite the fact that the government has detected SARS 2 in sewer systems, one of the early Covid symptoms is diarrhea, and SARS 1 had significant number of infections by fecal matter.
It seems to be a problem with older east Asian construction, I claim no specific expertise on the issue but I've observed poor p/u bend water barriers in even fairly nice buildings from the 70s and 80s in Taipei.
Fish tank filters are practically required for fish. I don't see why home air filters (HEPA) aren't more common especially in extreme environments with window opening not realistic.
You won't often catch covid from stray particles but from the person breathing next to you, which these filters can't help. This study was in a hospital where everyone is wearing serious PPE, so its a super edge case to get rid of covid in the air because the main use case of catching covid has been handle by plain old PPE.
This doesn't have sweeping applicability. It won't stop covid among the general population. Its for maybe hospitals that are on super covid lockdown that want a little more protection for their most vulnerable patients.
We get rid of covid through mass vaccination like any other virus. There's no shortcuts for those who refuse masks and vaccines.
how do you know? it seems like most cases are attributed to the nebulous "community spread" and nobody is really sure who they're coming from or how we're catching it. maybe we are getting it from the person breathing near us - if masks help, i don't see a reason that improved air filtration wouldn't.
All the data suggest that its not someone breathing on you in passing that's going to result in covid infection, but spending long periods with someone indoors in close proximity. Within a half hour in the massive grocery store? I would be shocked if you caught it. Drinking in someones living room, swapping stories within arms length, swapping spit flecks for 5 hours straight? Definitely going to spread everything you have in such a small enclosed space where the viral load is able to reach a much higher concentration over a long period of time.
> but spending long periods with someone indoors in close proximity.
It's not obvious to me that in-room air filters wouldn't reduce the exposure in this case, as the original commenter claimed? If it reduces the virus in the air, as the OP study finds, it seems like it probably would reduce virus exposure and thus infection rate when spending long periods indoors in close proximity, no?
Sure, just because it reduces the virus in the air doesn't necessarily mean it reduces infection -- like hypothetically the virus could commonny be going right from someone's exhale to someone else's inhale without having a chance to be filtered -- which I think is what the original commenter was suggesting -- but that's not the "spending long periods" scenario at all. I think it's true that while you probably can get infected in as little as ~15 minutes (not necessarily in just a couple minutes), but also clear that the longer you are in the same room, the higher risk.
But sure, we don't know exactly everything. All we can do is build knowledge one brick at a time, AND all we can do is act on the bricks we already have (that we don't have the whole wall yet is not a reason to avoid acting on our best picture (mixed metaphor, sue me) form what we do have)... but reducing virus in the air is a pretty huge brick for a respiratory infection. Based on everything we do know, it is hard to believe what the original commenter asks us to, to believe that reducing viral concentration in the air would NOT significantly lower infection rate.
I think it's becoming increasingly clear we should be spending at least as much attention on HEPA air filtration as people have been on masks.
yes, that's pretty much exactly what i'm saying: all the data we have is that it spreads exactly as you say, sitting with somebody for an extended period of time. because that's the sort of thing that people remember, and tell the contact tracers about.
but at least in my region, the majority of cases still don't have a known source. maybe that's because people are catching it in scenarios where they're in close proximity to somebody for extended periods of time but forget about it when the contact tracers call them, and all cases are spread that way.
or maybe it's spreading in grocery stores and other casual contact scenarios but that's just impossible to measure or count. we keep hearing that there's no evidence of it spreading in schools, and yet as long as students are in school it spreads a lot more among students. is it not spreading there, or is it just really difficult to find the evidence of that?
What data are you referring to? The protests and marches last year seem to be hard to ignore example of things that should have had more spread by these standards.
Those were outdoors with plenty of room for viral particulate to disperse. there has been a lot written about this, its called the infectious dose which is the amount of virus particulate needed for someone to become ill with the virus. I recommend pubmed or google scholar if you want a deeper dive.
if you are having trouble visualizing how this works, imagine a perfume dispenser jetting out a fine mist, that's your covid positive person exhaling. In an enclosed small room, the concentration of that particulate mist is much higher than in a large room, and unable to disperse quickly without any ventilation. Over time, you will inhale more and more of this particulate in this room at this concentration, and you will hit the infectious dose level eventually. If you are outside, or in a larger or well ventilated room, concentration of the particulate is much smaller since its either dispersing into a greater volume of air or being removed from the area due to ventilation, and it might take you a long period of time to inhale enough particulate at this comparatively lower airborne concentration in order to become sick. Outside, even in a protest, the volume of air is so large in which to disperse particulate that the risk of getting an infectious dose is negligible even with someone yelling right next to you.
Some of the marches that I went to... were less than airy, to be honest. Easily comparable to any ballgame I have been to.
So, I have seen a lot of these papers, but too much feels like post hoc justification. I'm game for being cautious, so I'm not really saying to do anything different, but I do want to urge way more caution in messaging than I'm seeing. It is fair and ok to talk of the uncertainty.
In terms of safety, vaccines are much better then getting COVID.
One of the big factors of "better protection" of immunity gained after recovering from the virus is survivor bias. In data about mortality after reinfection there are no people who died after getting it for the 1st time. This leaves only ones who had body strong enough to recover.
There's no surprise that later that group fares better.
What if the air is being actively refreshed and filtered. I believe this is what needs to start happening in most indoor environments. This would definitely help with reducing the amount of cases.
