closed no more
Disclaimer: This linked blog post is a great resource but remember to confirm what you read with several sources and not just the ones linked in an article.
The amount of virus it takes to be infected is said by experts to be an unknown as they are still studying this new virus and may be much lower than this blog post suggests – perhaps only 100 virus particles. So please only use what it says as starting point in doing your research.
As Massachusetts is starting to phase in reopening, with golf courses first, we all need to know how that might look and the safest ways to go back to work.
Dr Erin Bromage’s Blog has an excellent, informative post, along with graphs and diagrams, about how most people become infected with COVID-19, the various ways the virus is spread including which ways carry the most risk, how the bell curve works while we are in lockdown and how it will change upon reopening and best practices on phasing in opening non essential businesses.
It seems many people are breathing some relief, and I’m not sure why. An epidemic curve has a relatively predictable upslope and once the peak is reached, the back slope is also predictable. Assuming we have just crested in deaths at 70k, that would mean that if we stay locked down, we lose another 70,000 people over the next 6 weeks as we come off that peak. That’s what’s going to happen with a lockdown.
As states reopen, and we give the virus more fuel, all bets are off. I understand the reasons for reopening the economy, but I’ve said before, if you don’t solve the biology, the economy won’t recover.
There are very few states that have demonstrated a sustained decline in numbers of new infections. Indeed, the majority are still increasing and reopening. As a simple example of the USA trend, when you take out the data from New York and just look at the rest of the USA, daily case numbers are increasing. Bottom line: the only reason the total USA new case numbers look flat right now is because the New York City epidemic was so large and now it is being contained.
So throughout most of the country we are going to add fuel to the viral fire by reopening. It’s going to happen if I like it or not, so my goal here is to try to guide you away from situations of high risk.
Dr. Bromage’s research focuses on the evolution of the immune system, the immunological mechanisms responsible for protection from infectious disease, and the design and use of vaccines to control infectious disease in animals. He also focuses on designing diagnostic tools to detect biological and chemical threats in the environment in real-time.
Dr. Bromage joined the Faculty of the University of Massachusetts Dartmouth in 2007 where he teaches courses in Immunology and Infectious disease, including a course this semester on the Ecology of Infectious Disease which focused on the emerging SARS-CoV2 outbreak in China.
Dr. Bromage’s blog is a fascinating and thought-provoking read. Thanks for posting it. On the one hand, it gives me hope that we can manage some thoughtfully planned small gatherings outdoors over the coming months and that the re-opening of golf clubs was reasonable. On the other hand, it raises strong doubts in my mind that indoor events or gatherings, even when people are separated by 10 ft or so, can be made safe due to contained environments and controlled air flows. His examples appear to be well documented. Read the blog! Click through to the sources and read some more.
I agree Anne. This is the most informative, actionable, useful information I’ve seen so far about Covid-19.
Thanks for posting Marti.
@Anne Larner, I agree, this is a sobering but informative blog. Very bad news for indoor restaurants. Even if masks work, one can’t very well eat a meal while wearing one. Let’s hope masks prove to help for other indoor gathering places.
@Marti, it would be great to start making decisions informed by this insight but I’m curious as to why you’re singling out this particular blog for its excellence?
As the author says about himself, “I am not claiming to be an expert in coronaviruses, medicine, or preparedness.”
And as Scopus says about the author, “h-index = 16.”
Likewise I am not claiming to be an expert, but as with so many other bold proclamations floating around the Internet on this topic, I would counsel the taking of a single granular particle containing approximately 1.2 quintillion ions of Na+ and Cl-.
Michael, I chose this blog because of Dr Bromage’s vast experience with immunological research, focus on designing diagnostic tools to detect biological and chemical threats in the environment in real-time and his work on the ecology of infectious disease using COVID-19 – all of which is above.
Also because it hits on issues most people need to know and gives suggestions for reopening.
I would never suggest information be taken from only one place but this blog is a good one to add to the mix. I found it very informative.
I’ve been reading this blog for a while as I have been wondering about businesses reopening. I’m not convinced that reopening states is a good idea yet but I don’t see why some other local businesses couldn’t reopen the same way pharmacies and small eateries now offering groceries do.
It seems to me that small, locally owned business could reopen using the “order and pay online with curbside pickup” practice. These could be book stores, puzzle and game stores, gift shops – just about any small, local retail store.
Thanks Marti, I also found the article to be very informative, especially the claims about infection being a function of exposure over time –
and
and
Almost nobody else seems to be credibly proposing these theories, and based on everything I’ve read, they fly in the face of what we’ve been told by the CDC. If true, then I feel like I personally have been overreacting and I really need to relax my cautiousness!
But I’ve had the chance to go back through the blog post and based on a review of the references, I couldn’t locate any scientific basis or supporting evidence for the article’s foundational claims of:
and
Also, to be honest I’m a bit uncomfortable with the way the blog is presented – the references were evidently added in after the fact; the article has been continuously “updated”; and the comments section contains only praise and simple questions about when people will be able to get back to operating their doggie daycares and hot yoga spas, rather than the robust scientific discussion that you’d expect in response to new claims like this.
Also, I wasn’t able to find any scholarly articles by Dr. Bromage on human viral transmission -his published work seems to have focused almost exclusively on rainbow trout, salmon, herring, and barramundi (an extremely delicious Australasian fish).
In case I’ve mischaracterized anything, I’d be most grateful to be corrected – as I mentioned, I’d love to revise (relax?) my behavior based on the viral time-exposure theories presented in this blog, but given the above concerns I’d be uncomfortable doing so.
Ok Michael, I did more research and have found nothing to support the parts of the above blog you have pointed out. In fact I’ve found experts who say infection takes far less viral exposure, maybe just 100 virus particles. Thank you for the correction.
I first thought I would just take down the post but then I decided to leave it up with a disclaimer.
The blog has some interesting and relevant observations, but I think the number of particles topic is a sidetrack. What matters is much more macro. We know the virus is likely more contagious that the flu and much less than other known diseases such as hand, foot, and mouth disease and measles. We have pretty strong evidence that supermarkets aren’t hotspots (locations of high risk) for customers at this time, but that employees have gotten sick. I don’t believe we know if supermarket employees are at greater risk than other people who aren’t staying home. We haven’t observed significant, if any, transmission from people passing each other outside. I am not sure there’s publications on it yet, but healthcare workers appear to be better protected if their institutions require masks. We know superspreading events occur, the exact transmission vector is not currently fully understood, and that indoor air is suspect enough that masks inside are prudent. All of those observations compiled across all the countries that have had earlier peaks has led to our current state recommendations, which are by definition simplified but also seem prudent.
We don’t fully understand this virus, but we have a lot of experience with disease transmission. We aren’t starting from scratch. We are doing a reasonable job in the state.
I just asked for credentials but want to add that Bromage has made a good effort to describe degrees of risk in a way that seems helpful. But reading Bowen seems like an essential add on. Good idea not to trust time brevity as a necessarily significant Defense.
@Mike Halle, I strongly disagree that raising concerns about the blog is a “sidetrack.” The author uses the particle estimate as the basis for a dose/time theory of the physics of infection which at this point seems to be nothing more than conjecture.
The blog’s references offer no scientific basis for the 5-minute “airstream” or “face-to-face talking” absorption scenarios, and it strikes me as quite dangerous to be proposing them because if they are true, then many people (including myself) would adjust and relax their behavior accordingly.
As you point out, we do have a lot of experience with disease transmission. But I couldn’t find any credible research validating the blog’s theory of an infectious threshold of cumulative viral particle inhalation measured in minutes.
I would be elated if you were to have better luck, because it’s certainly a fascinating theory. But until it’s proven it’s also a dangerous one.
Michael, I suspect we’re agreeing more than disagreeing as to the practical importance of particle estimation. You just see it as dangerous, I see it at not very relevant or useful in making decisions. At the highest level, though, more virus worse, less virus better. Small, confined spaces with limited air circulation worse, open air better. Sustained exposure to virus-laden environment bad, transient exposure better.
There’s definitely literature in disease modeling covering time vs dose. Search for “dose response time infection”. For instance, this paper gives a good overview or the mathematical models (reader alert, high geek factor):
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5400279/
The point I tried to make is that the paper’s focus on exact number of particles is not that relevant to our public health or self education-oriented discussion, since other variables may swamp the exact microbe counts anyway. More important is the the epidemiology of the disease that we can observe in other places.
It is a standard part of a disease model to assume that risk of infection is proportional to amount of virus or bacteria present and inversely proportional to the duration of exposure. This is a purely statistical relationship. However, the exact relationship of dose, response, and time may is not generally linear. There also happen to be a lot more practical variables involved as well: how long the virus or bacteria are viable, how likely they are to be transmitted through a particular vector, how likely they are to get where they need to be in the body (upper or lower respiratory tract, digestive tract, etc), how the human body in general and specific individuals are able to fight the disease. Those variables make a huge difference in modeling a specific disease spreading in the real world.
Relative concentration of virus and viral exposure over time may or may not also have something to do with severity of contracted illness. Several preliminary studies suspect that may be true of COVID-19, possibly explaining why young Chinese physicians were early casualties of the disease. This is an area where we don’t yet have enough information.
As for outside locations in general with COVID-19, there is emerging information. There is a Chinese preprint looking at contact traced infections outside of Wuhan that found all but two were from indoor settings, and those two individuals were infected in a face-to-face discussion. This, again, is broadly compatible with what we know about COVID-19, other coronaviruses, and disease transmission in general: outdoors it safer than indoors, and transient passing exposure is less risky than sustained face-to-face talking. We know from Mount Vernon, Washington that group singing may lead to group transmission inside, even when social distancing is in place.
Is this all different from the CDC guidelines? Not really. The CDC and state guidelines have to be simplified so that any person can understand them, and provide most people with most protection. Six foot rule: easy to understand, reasonable general compromise. However, it won’t be appropriate if you’re in a small space with a person sneezing at you. Nor it is designed to model a normally-breathing person briefly passing four feet from you outside. But it’s still a reasonable rule a reasonable amount of the time.
What that means to me is that you stick with the CDC/state guidelines but understand where they are over- or under-protecting you so you can take additional action or, in other situations, reduce your concern over exposure to yourself from others. For example, most people shouldn’t fear going outside because of accidental exposure, to the point of not exercising regularly or becoming stir-crazy. Similarly, they shouldn’t be harming themselves through diet because of a fear of the grocery store (if no other options for shopping exist).
Thanks Mike, that’s extremely informative and thoughtful.
With regard to “dose response time infection,” my interpretation is that this deals with the concept of administering a “dose” of pathogen instantaneously vs. administering it over an extended period of time, and that this concept is more concerned with the probability of infection, which is higher in the former scenario and lower in the latter scenario because the immune system would be less overwhelmed:
I’m having trouble grasping how this relates to the blog’s seemingly risk-agnostic theory that COVID-19 infection occurs whenever a cumulative threshold of particle inhalation is surpassed. This implies that it may take 5 minutes to inhale n particles or it may take 20 minutes, but once n particles are inhaled, then infection will occur – the blog’s author proposes, “Remember the formulae: Successful Infection = Exposure to Virus x Time.”
If anything, Brouwer seems to conclude just the opposite, i.e. that unlike radiation and chemical exposure, pathogen infection is single-hit and does not need to accumulate.
If you get the chance could you share your insight into how I might be misinterpreting this?
PS Mike, I do agree with your “macro” points on COVID-19 epidemiology, which are indeed a much more important consideration than the physics of transmission.
Michael, I guess I am so used to trying to process the torrent of preliminary and possibly-related and un-peer reviewed information coming out, I am not focused on the failings of one specific work, but instead where their aggregate strengths point us. If I were one of Dr. Bromage’s peer reviewers, I would have to think differently, but I am not qualified for that role.
The best I can do as a scientist, engineer, and citizen is to help others find the reasonable center in this Mass of sometimes conflicting information. It is also rewarding to learn along the way. Wish is wasn’t about stuff so life and death for our community.
Sorry, that last sentence should say, I wish we were dealing about issues that were not so “life and death” for members of our community.
Marti, I appreciate you linking to an article that many of us scientists have been using because of its accessibility to the public, excellent communication, and clear factual basis. However, I do not think your disclaimer about the minimum number of viral particles serves any useful purpose. It is academic and unimportant whether the actual number is 100, 200, or 1000. These are all within a small range of error, and since it is a statistical determination, does not change the message of the blog. The correct number, when determined by multiple scientists, will have a considerable confidence interval that is influenced by the path of entry, host age and genetics, and other factors we don’t even know about yet.
Those that choose to attack the author for the pettiest of details are choosing to launch a message of disinformation. Please do not contribute to this by saying the entirety of the post is suspect. In fact, it is not suspect and is well-backed by the literature that is cited within.
I have been working with infectious disease specialists to try to better inform the public of scientific facts related to SARS-COV-2 and COVID-19. We are under a full attack right now from special interests groups of all kinds: anti-vaxxers, conspiracy theorists, libertarians, and foreign agents trying to sow discord. Unfortunately some of those elements exist in our community as well. I’m highly concerned that this post is now causing more harm than good.
@Sheldon, I strongly support a continued shutdown and the author’s overall message of caution.
My complaint is that the following estimates of time-to-infection put me, the reader, at great risk by promoting a false sense of security without offering any scientific evidence:
– Being in a room with someone who’s infected: 50 minutes in a “modest-size” room with “general breathing,” but only if “every virus ended up in your lungs.”
– Speaking with someone who’s infected: 5 minutes of speaking “face-to-face”
– Joggers: 5+ minutes of “being in their airstream”
– Hiking: 3 hours of “drafting someone” could potentially lead to infection
From the New York Times Newsletter
“ 3. Why a virus blog post went viral
By now, a friend may already have forwarded you a much-discussed blog post from a biologist named Erin Bromage — it has more than six million views.
It’s an impressively clear explanation of how the virus often spreads inside confined spaces, like restaurants, churches, workplaces and schools.
Even when people remain more than six feet apart, they can become infected by breathing the same air as an infected person for an extended period of time, Bromage explains. Those scenarios, he argues, are more worrisome than a quick trip to the grocery store or almost any outdoor activity.
Background: Bromage told me that he began focusing on the virus in January to have a current example to use in his class on infectious diseases at the University of Massachusetts, Dartmouth.”
Thank you Mike and Michael for carrying this discussion to a deeper level in an informative and professional way. I’m trying to find the signal in all the coronavirus noise flying about these days and this really helps. I’m awash in experts, pseudo-experts and competing data models. All I’m trying to do is understand better so I can make good decisions for myself and my family.
Dr. Bromage’s hypothesis, observations, and claims in the blog would be easier to assess if they had been subject to peer review. That’s an importance check and balance on science, no different from anyone else. To his credit, Dr. Bromage isn’t misrepresenting his work or his expertise (see https://www.erinbromage.com/ ). His observations are apparently, however, getting a lot of attention and press. It would benefit everyone if they were vetted and discussed by peers.
This isn’t an attack in any way on the research or the person. These are questions we must always ask. Indeed, as scientists it is our responsibility to ask those questions. Lay people should have good AND debatedAND validated science upon which to form opinions and make decisions.