I was thinking along these same lines but for skin-microbiota… we are lagging behind understanding this compared to gut-microbiota but it seems like the diversity is pretty important to our overall health? Its probably only a risk worth considering for the “install it in all the offices” rather than against using far-UVC in pandemic situations, but I guess research would be needed to assess the risks for skin disorders, or whatever else these microbiota might be important for?
That’s likely an even smaller issue. Far-UV inactivates the transient microbiome on the upper skin surface but not in the pores where the majority of the bacteria live. It’s also strictly line of sight and the skin is pretty wrinkly and only small areas (e.g., back of the hands) are exposed and you constantly re-seed your microbiome from other parts of the body. There’s prelim data from hairless mice which found no changes to the microbiome.
I agree with Jasper and don’t expect impacts on the skin microbiome to be a big deal, but it would, of course, be good to get some more data.
One useful comparison is that healthcare workers use alcohol-based hand sanitizers many times a day, which are quite potent and can kill microbes in areas inaccessible to Far-UVC.
In this review paper, they only saw changes to the composition of the skin microbiome after extremely frequent daily hand disinfection:
“Overall microbe diversity on hands was unchanged with alcohol-based hand rub use or hand washing, with the exception that overall diversity was lower in those that reported >40 hand washing with soap and water events per shift”
From Edmonds-Wilson et al. 2015. I don’t know how bad reduced diversity is and what harmful effects that might have.
While these alcohol-based hand sanitizers are quite effective, they evaporate quickly and accordingly kill microbes in a very short time span. In certain scenarios, you could imagine far-UVC being different because it could kill off skin microbes at the back of your hands more or less continuously during the ~8 hours you are at work. This raises the question if this mode of continuous disinfection has different effects than the short bursts of frequent hand disinfection experienced by healthcare workers. I’d be surprised if the outcome is very different.
Indeed, I think part of the path to impact for far-UVC will be that adoption will hopefully be driven by, e.g., employers like Google equipping their offices with far-UVC lamps because they expect this to reduce the total number of sick days of their workers and therefore increase productivity + profits. Getting this type of evidence for efficacy would be great since it would be an excellent sales pitch to companies whose employees earn a lot, meaning sick days are costly. Ideally, you would be able to tell them something like, “Installing these far-UVC fixtures in the whole office will cost you $30,000, but based on existing evidence and our best models, you’ll likely recoup those costs after approx. 18 months due to a reduction in sick days of your employees.”
Presumably, that would be a big boost for demand and competition, thereby reducing costs and increasing R&D. It could help to make far-UVC widespread enough to make a difference in stopping future outbreaks or slow down the spread of disease during the next pandemic.
but could it exacerbate pandemic risk by reducing immunity, thereby making it easier for a bioweapon engineer to create a scary pathogen?
There has been very little research on the interaction of far-UVC and the immune system. It is a topic that often comes up in discussions around far-UVC safety and is related to the well-known “hygiene hypothesis,” which says something like, “If you’re not exposed to enough germs as a child, you might get more allergies.”
I want to see more research on this, but so far, it hasn’t been as much of a priority. First, people wanted to figure out things like whether far-UVC could give you skin cancer or make you blind. By now, we know those things won’t happen, so we can turn to more “second-order” type risks like immune system effects.
However, I have a few intuitions about why this seems unlikely. First of all, it is an “end-game” worry in the sense that it seems like it would only become relevant once far-UVC is almost ubiquitous. Even if it becomes widespread, it would be installed in places like hospitals, shared offices, public transport, etc., but you probably wouldn’t have it in your home or anywhere outside. Let’s say you would spend ~10 h per day in environments that have much more sterile air than nowadays, but the other ~14 h, you’re at home or wherever and still exposed to the germs of, e.g., your partner or children.
Also, I expect that even widespread far-UVC wouldn’t reduce fomite transmission much because its disinfection works by line of sight and is easily shielded. So your immune system would still be challenged by that type of transmission.
As I wrote in the post, we only really care about far-UVC if we can find a path to really widespread adoption and high enough doses to slow down or even stop the transmission of extremely infectious agents like measles. If we actually achieve pathogen suppression that strong, I find it hard to imagine a malevolent actor engineering a pathogen so scary that it overwhelms this system. Remember that far-UVC would only be one of our defenses against pandemics and would be combined with PPE, ventilation, medical countermeasures, etc.
I also haven’t seen any convincing evidence that a reduction in your exposure to germs dramatically worsens your immune system. While I haven’t looked into it deeply, the hygiene hypothesis seems to be somewhat controversial and concerns things like allergies, not, e.g., doubling your susceptibility to common infections because of a worse immune system.
Similarly, I have heard claims that due to all the social isolation, masking, etc., during the Covid pandemic, peoples’ immune systems got worse. Yes, the flu + RSV season peaked earlier last winter and was decently bad, but I don’t see how this can be attributed to a broad decrease in immune competency. Rather, it just seems like many people weren’t exposed to these specific pathogens that they would have typically been challenged with more frequently. I’m not terribly knowledgeable here, so might be mistaken, would be curious if other folks have more insights.
The “hygiene hypothesis” is a complicated topic, so I’m not sure what the net balance would be:
cumulative RSV cases were, I believe, lower throughout the pandemic, even accounting for the later peak
common respiratory infections may not be so harmless, with e.g. flu recently being linked to increased risk of a bunch of diseases (https://www.cell.com/neuron/pdf/S0896-6273(22)01147-3.pdf), viruses anecdotally causing chronic illnesses such as ME/CFS and POTS (similar to Long Covid), and increasing evidence that many of these viruses actually persisting in the human body (like 12/22 MS patients having seasonal coronaviruses in their brain: https://pubmed.ncbi.nlm.nih.gov/1596089/) that can’t be good.
similar viruses affect immunity towards each other. In some cases, this is helpful. A recent article found that people who remained asymptomatic with COVID were likely to have specific memory T cells from seasonal coronaviruses. On the other hand, this imprinting can go awry, when memory cells are ineffective against the new virus, and a broad antibody response to seasonal coronaviruses is actually a risk factor for Long Covid (and I believe severe covid as well) https://www.medrxiv.org/content/10.1101/2022.11.07.22282030v1.full-text
So I think this hygiene effect would be great for public health, but it might increase tail risk? Then again, the stronger hygiene there is, the harder it will be for (airborne) pandemics to occur, so I’d really expect it to be net positive.
Everything touched by the immune system is complicated, agree. But I strongly suspect the net balance will be highly positive, still:
a) As you wrote, seasonal respiratory disease is a massive problem, in the order of trillions of dollars of health and economic damage every year
b) There is some cross-reactivity, yes, but the tail events will be too different from what we usually have. Frequent common-cold exposure will not be the thing that protects us from a GCBR. Neither will the original antigenic sin play a role, as that usually requires quite closely related strains to matter. Overall, your immune system will be a bit less-well prepared for this particular pathogen family that you haven’t encountered in a while, but that’s also the case for any other sufficiently different pathogen.
Just a couple of lay person observations to add here regarding the hygiene hypothesis:
So far it seem hygiene interventions like hand washing, clean water, etc. have been net positive so based on this I think there is cause for optimism around more hygiene interventions. I think the scenario where decreasing infection is possibly harmful is in completely sterile environments but as others have pointed out, far-UVC seems unlikely to eliminate all pathogens we come into contact with. Also, I understand the hygiene hypothesis to be about increasing prevalence of allergies in cleaner environments but I remember reading that we are learning that only specific pathogens are responsible for reducing allergies and not that it is a lack of high levels of exposure to a wide array of diseases
I think I have heard that certain infections can actually weaken your immune system. For example, Harvard Health says that avoiding infection is part of strengthening one’s immune system. I am thinking (and experts have probably explored this) that perhaps one contributing factor to increased infection after lock downs was that covid had weakened people’s immune systems.
Harvard Health says that avoiding infection is part of strengthening one’s immune system
I was intrigued so looked at the link. It has heading “Healthy ways to strengthen your immune system” and says in one bullet point under this “Take steps to avoid infection, such as washing your hands frequently and cooking meats thoroughly”, but doesn’t say anything about why this would help strengthen the immune system (it just links to a page with steps for reducing infection risk). A possible alternative interpretation is that this is meant as advice for not getting sick rather than making the immune system more effective, and this seems more likely to me. But it’s not clear.
Agreed—I wished I could learn more. In any case, I feel really uncertain about the hygiene hypothesis. Given that the advice to “collect bugs” for increased immunity is so widespread and even propagated by doctors it baffles me that it is so hard to find evidence for this advice. The advice also has serious bearing on people’s well-being which is another reason that this claim should be investigated much more closely.
I’ve wondered about the interaction between far-UVC and immunity:
as well as protecting us against a scary novel pandemic-level pathogen, far-UVC would also kill off germs for various “common or garden” infections
at first glance, this sounds like a pretty great cherry on the cake
but could it exacerbate pandemic risk by reducing immunity, thereby making it easier for a bioweapon engineer to create a scary pathogen?
I was thinking along these same lines but for skin-microbiota… we are lagging behind understanding this compared to gut-microbiota but it seems like the diversity is pretty important to our overall health? Its probably only a risk worth considering for the “install it in all the offices” rather than against using far-UVC in pandemic situations, but I guess research would be needed to assess the risks for skin disorders, or whatever else these microbiota might be important for?
That’s likely an even smaller issue. Far-UV inactivates the transient microbiome on the upper skin surface but not in the pores where the majority of the bacteria live. It’s also strictly line of sight and the skin is pretty wrinkly and only small areas (e.g., back of the hands) are exposed and you constantly re-seed your microbiome from other parts of the body. There’s prelim data from hairless mice which found no changes to the microbiome.
I agree with Jasper and don’t expect impacts on the skin microbiome to be a big deal, but it would, of course, be good to get some more data.
One useful comparison is that healthcare workers use alcohol-based hand sanitizers many times a day, which are quite potent and can kill microbes in areas inaccessible to Far-UVC.
In this review paper, they only saw changes to the composition of the skin microbiome after extremely frequent daily hand disinfection:
From Edmonds-Wilson et al. 2015. I don’t know how bad reduced diversity is and what harmful effects that might have.
While these alcohol-based hand sanitizers are quite effective, they evaporate quickly and accordingly kill microbes in a very short time span. In certain scenarios, you could imagine far-UVC being different because it could kill off skin microbes at the back of your hands more or less continuously during the ~8 hours you are at work. This raises the question if this mode of continuous disinfection has different effects than the short bursts of frequent hand disinfection experienced by healthcare workers. I’d be surprised if the outcome is very different.
Hi Sanjay, thanks for the comment!
Indeed, I think part of the path to impact for far-UVC will be that adoption will hopefully be driven by, e.g., employers like Google equipping their offices with far-UVC lamps because they expect this to reduce the total number of sick days of their workers and therefore increase productivity + profits. Getting this type of evidence for efficacy would be great since it would be an excellent sales pitch to companies whose employees earn a lot, meaning sick days are costly. Ideally, you would be able to tell them something like, “Installing these far-UVC fixtures in the whole office will cost you $30,000, but based on existing evidence and our best models, you’ll likely recoup those costs after approx. 18 months due to a reduction in sick days of your employees.”
Presumably, that would be a big boost for demand and competition, thereby reducing costs and increasing R&D. It could help to make far-UVC widespread enough to make a difference in stopping future outbreaks or slow down the spread of disease during the next pandemic.
There has been very little research on the interaction of far-UVC and the immune system. It is a topic that often comes up in discussions around far-UVC safety and is related to the well-known “hygiene hypothesis,” which says something like, “If you’re not exposed to enough germs as a child, you might get more allergies.”
I want to see more research on this, but so far, it hasn’t been as much of a priority. First, people wanted to figure out things like whether far-UVC could give you skin cancer or make you blind. By now, we know those things won’t happen, so we can turn to more “second-order” type risks like immune system effects.
However, I have a few intuitions about why this seems unlikely. First of all, it is an “end-game” worry in the sense that it seems like it would only become relevant once far-UVC is almost ubiquitous. Even if it becomes widespread, it would be installed in places like hospitals, shared offices, public transport, etc., but you probably wouldn’t have it in your home or anywhere outside. Let’s say you would spend ~10 h per day in environments that have much more sterile air than nowadays, but the other ~14 h, you’re at home or wherever and still exposed to the germs of, e.g., your partner or children.
Also, I expect that even widespread far-UVC wouldn’t reduce fomite transmission much because its disinfection works by line of sight and is easily shielded. So your immune system would still be challenged by that type of transmission.
As I wrote in the post, we only really care about far-UVC if we can find a path to really widespread adoption and high enough doses to slow down or even stop the transmission of extremely infectious agents like measles. If we actually achieve pathogen suppression that strong, I find it hard to imagine a malevolent actor engineering a pathogen so scary that it overwhelms this system. Remember that far-UVC would only be one of our defenses against pandemics and would be combined with PPE, ventilation, medical countermeasures, etc.
I also haven’t seen any convincing evidence that a reduction in your exposure to germs dramatically worsens your immune system. While I haven’t looked into it deeply, the hygiene hypothesis seems to be somewhat controversial and concerns things like allergies, not, e.g., doubling your susceptibility to common infections because of a worse immune system.
Similarly, I have heard claims that due to all the social isolation, masking, etc., during the Covid pandemic, peoples’ immune systems got worse. Yes, the flu + RSV season peaked earlier last winter and was decently bad, but I don’t see how this can be attributed to a broad decrease in immune competency. Rather, it just seems like many people weren’t exposed to these specific pathogens that they would have typically been challenged with more frequently. I’m not terribly knowledgeable here, so might be mistaken, would be curious if other folks have more insights.
The “hygiene hypothesis” is a complicated topic, so I’m not sure what the net balance would be:
cumulative RSV cases were, I believe, lower throughout the pandemic, even accounting for the later peak
common respiratory infections may not be so harmless, with e.g. flu recently being linked to increased risk of a bunch of diseases (https://www.cell.com/neuron/pdf/S0896-6273(22)01147-3.pdf), viruses anecdotally causing chronic illnesses such as ME/CFS and POTS (similar to Long Covid), and increasing evidence that many of these viruses actually persisting in the human body (like 12/22 MS patients having seasonal coronaviruses in their brain: https://pubmed.ncbi.nlm.nih.gov/1596089/) that can’t be good.
similar viruses affect immunity towards each other. In some cases, this is helpful. A recent article found that people who remained asymptomatic with COVID were likely to have specific memory T cells from seasonal coronaviruses. On the other hand, this imprinting can go awry, when memory cells are ineffective against the new virus, and a broad antibody response to seasonal coronaviruses is actually a risk factor for Long Covid (and I believe severe covid as well) https://www.medrxiv.org/content/10.1101/2022.11.07.22282030v1.full-text
So I think this hygiene effect would be great for public health, but it might increase tail risk? Then again, the stronger hygiene there is, the harder it will be for (airborne) pandemics to occur, so I’d really expect it to be net positive.
Everything touched by the immune system is complicated, agree. But I strongly suspect the net balance will be highly positive, still:
a) As you wrote, seasonal respiratory disease is a massive problem, in the order of trillions of dollars of health and economic damage every year
b) There is some cross-reactivity, yes, but the tail events will be too different from what we usually have. Frequent common-cold exposure will not be the thing that protects us from a GCBR. Neither will the original antigenic sin play a role, as that usually requires quite closely related strains to matter. Overall, your immune system will be a bit less-well prepared for this particular pathogen family that you haven’t encountered in a while, but that’s also the case for any other sufficiently different pathogen.
Just a couple of lay person observations to add here regarding the hygiene hypothesis:
So far it seem hygiene interventions like hand washing, clean water, etc. have been net positive so based on this I think there is cause for optimism around more hygiene interventions. I think the scenario where decreasing infection is possibly harmful is in completely sterile environments but as others have pointed out, far-UVC seems unlikely to eliminate all pathogens we come into contact with. Also, I understand the hygiene hypothesis to be about increasing prevalence of allergies in cleaner environments but I remember reading that we are learning that only specific pathogens are responsible for reducing allergies and not that it is a lack of high levels of exposure to a wide array of diseases
I think I have heard that certain infections can actually weaken your immune system. For example, Harvard Health says that avoiding infection is part of strengthening one’s immune system. I am thinking (and experts have probably explored this) that perhaps one contributing factor to increased infection after lock downs was that covid had weakened people’s immune systems.
I was intrigued so looked at the link. It has heading “Healthy ways to strengthen your immune system” and says in one bullet point under this “Take steps to avoid infection, such as washing your hands frequently and cooking meats thoroughly”, but doesn’t say anything about why this would help strengthen the immune system (it just links to a page with steps for reducing infection risk). A possible alternative interpretation is that this is meant as advice for not getting sick rather than making the immune system more effective, and this seems more likely to me. But it’s not clear.
Agreed—I wished I could learn more. In any case, I feel really uncertain about the hygiene hypothesis. Given that the advice to “collect bugs” for increased immunity is so widespread and even propagated by doctors it baffles me that it is so hard to find evidence for this advice. The advice also has serious bearing on people’s well-being which is another reason that this claim should be investigated much more closely.