The Bromage Protocol: Infectivity = People X Duration X Proximity X Enclosure X Air Stagnation
The following blog post by Dr. Erin Bromage provides his assessment of the relative risks of contracting the COVID-19 virus at various activities and settings. In this article I will critique his information and provide my conclusion that we can resume all outdoor low-population, low proximity/duration activities, including businesses, and should bring fresh air into all indoor businesses. If his assessment is correct, failing to do so risks unnecessarily doing more damage to our economy and mental well-being.
Dr. Bromage is an Associate Professor of Biology at the University of Massachusetts Dartmouth where he teaches courses in Immunology and Infectious disease. The information in his blog post was credible enough that he was interviewed on the MSNBC show, The Last Word, with Lawrence O’Donnell on May 11, 2020.
I believe the information in his article is desperately important to recovering our economy, and also our mental health. So I’ve created the following point-by-point annotation of it. And, in the unashamed hope of amplifying it— there’s a word we didn’t all use much before 2018 — I’m calling it the Bromage Protocol, even though he himself expresses no such thing.
My Analysis and Comments
I regard Dr. Bromage’s article as ‘scientific opinion’ based on scientific fact. But since it is from a career immunologist, it’s pretty strong information. I have done this writeup because I believe, if the statements by this credible scientist are true, it tells us that …
- We can go to outdoor businesses with very low risk of contracting the virus.
- Businesses and events should use substantial forced air ventilation.
- Businesses should open their doors and windows.
- We don’t have to be afraid of one another outdoors, except being directly coughed or sneezed upon.
Warning about eyes: Note that one aspect of transmission that is not strongly addressed in the article is the possibility of the virus entering our system through our eyes. Dr. Bromage mentions it just once in his discussion of particle counts: “…infectious viral particles you receive in one breath or from one eye-rub.”We’ve all learned that the virus is a respiratory virus… one of breathing. And we’ve been told that food is not much of a risk. But it’s been pounded into all of us that we must not touch our faces after touching surfaces… because of the possibility of bringing the virus onto our various mucous membranes, by which the virus might infect us. So if that’s the case, then isn’t it logical that the virus, when it is in the air momentarily from any coughing, sneezing, or even breathing, might land on our eyes. I am adding this caveat to make sure that we don’t all think that masks alone make ANY environment 100% safe, indoor, outdoor, ventilated or not.
Bromage Excerpt 1: In order to get infected you need to get exposed to an infectious dose of the virus; based on infectious dose studies with other coronaviruses, it appears that only small doses may be needed for infection to take hold.
JB: Wow, scientists actually study the specific amount of a virus that is needed to cause an infection! Who knew? Apparently you do not get infected by merely having one single virus particle, called a virion, enter your body. Think about the alternative… that single particles could overwhelm any species’ defenses: if this were nature’s way, I’d imagine that whole species would be frequently wiped out.
Bromage Excerpt 2: Some experts estimate that as few as 1000 SARS-CoV2 infectious viral particles are all that will be needed (ref 1, ref 2).Please note, this still needs to be determined experimentally, but we can use that number to demonstrate how infection can occur.
JB: I’m just calling to your attention the fact that scientists simply DO NOT KNOW how many virus particles are the infectious dose for the current pandemic. Bromage’s entire article is predicated on this concept of a minimum dosage, and it’s an unknown number. But we are an advanced civilization, capable of balancing this imperfect knowledge against the body of ‘experience’ in the real world, after seeing 300,000 deaths worldwide and what we can reasonably judge from how those cases occurred, meaning all of the scientific studies and anecdotal information.
Bromage Excerpt 3: Infection could occur, through 1000 infectious viral particles you receive in one breath or from one eye-rub, or 100 viral particles inhaled with each breath over 10 breaths, or 10 viral particles with 100 breaths. Each of these situations can lead to an infection.
JB: If true, the number of particles for an infectious dose accumulates over time. This brings up the question, over what period of time? In a blog response he speculates this would be during a day, not over the course of days. Having read two books on bacteria and viruses, below, I think what’s going on here is that the body fights off invaders all day, every day. When more invaders arrive than can be fought off, they win. And our defender cells are constantly replenishing. Hmmm, this thing about sleeping — quarantining yourself — for eight hours every day (so your defensive fortifications can be replenished) is starting to make sense.
Bromage Excerpt 4: Treat public bathrooms with extra caution (surface and air), until we know more about the risk.
JB: Although Bromage concludes nothing about bathrooms, the lesson with bathrooms is much easier than other, more social venues: don’t touch your mucous membranes after touching surfaces in ANY highly visited place, and let fresh air in first. The goal, as we’ll conclude from the totality of the article, is to breathe only fresh air.
Bromage Excerpt 5: A single cough releases about 3,000 droplets and droplets travels at 50 miles per hour. A single sneeze releases about 30,000 droplets, with droplets traveling at up to 200 miles per hour. A single breath releases 50–5000 droplets. Most of these droplets are low velocity and fall to the ground quickly.
JB: So, to summarize his info on what are called “violent expiratory events,” here’s the list of how much germ our various actions spew out, in order from most to least:
Sneezing > Coughing > Yelling/Singing > Talking > Breathing
Bromage Excerpt 6: Studies have shown that a person infected with influenza can releases up to 33 infectious viral particles per minute.
JB: Wow #2: They actually have scientific evidence that particles are released at a particular rate. These scientist folks probably have a number for everything! What do they do, spend all day just measuring one thing after another?
Bromage Excerpt 7: Remember the formula: Successful Infection = Exposure to Virus x Time
JB: Now his formula starts to build. Danger=“particles” times “duration.” Your high-school math teacher, in an effort to confuse you, would say that “infection is a function of particles and duration.” Duration is pretty simple, the length of time you’re exposed to particles. But exposure, which I’m calling particles at the moment, is more complicated. It has several ingredients. The rest of the article will essentially be breaking it out into its constituent parts.
Bromage Excerpt 8: The exposure to virus x time formula is the basis of contact tracing. Anyone you spend greater than 10 minutes with in a face-to-face situation is potentially infected. Anyone who shares a space with you (say an office) for an extended period is potentially infected.
JB: When you hear about contact tracing, he’s telling us that they won’t try to contact everyone, just those with whom you spend at least 10 minutes. So that’s merely an educated guess on the ‘danger zone,’ amount of time… but it’s the same educated guess that is used by the people trying to save our lives every day.
Bromage Excerpt 9: You can be shedding the virus into the environment for up to 5 days before symptoms begin.
JB: This article is about particle quantity for infection, not the general science of the epidemic, but this little morsel was important enough for me to call out: we simply can’t judge a person’s contagiousness by their appearance of health.
Bromage Excerpt 10: Ship outbreaks, while concerning, don’t land in the top 50 outbreaks to date.
JB: Interesting to know. Most of us presume that cruise ships are ‘the worst’ but on a statistical basis, they’re not the problem.
Bromage Excerpt 11: Ignoring the terrible outbreaks in nursing homes, we find that the biggest outbreaks are in prisons, religious ceremonies, and workplaces, such as meat packing facilities and call centers. Any environment that is enclosed, with poor air circulation and high density of people, spells trouble.
Three new elements are presented here as ‘facts’: enclosed spaces, poor air circulation, high density of people. The first two are almost identical, but notice that you can have an enclosed space such as an airplane that has terrific circulation, so they really are two separate matters.
“Density of people” is actually two things. It implies proximity and crowd size. In fact, what we were previously calling “particles” in the formula is mostly the crowd size, since it’s the people who generate the particles.
Bromage Excerpt 12: Restaurants: Some really great shoe-leather epidemiology demonstrated clearly the effect of a single asymptomatic carrier in a restaurant … Approximately 50% of the people at the infected person’s table became sick over the next 7 days. 75% of the people on the adjacent downwind table became infected.
JB: This establishes that air is the most likely vehicle… at least in a restaurant. Does that mean that touch transmission doesn’t happen, or isn’t possible? No. But fear of touch transmission is not what’s shutting down economies around the world. We can wash our retail purchases if we want. We can avoid touching our faces. This is a fascinating thing to work through the mental gymnastics. If scientists categorically established back in February, that this disease only transmitted on surfaces, we wouldn’t have shut a single business. We’d just be disinfecting the hell out of things, and probably all start wearing some new types of gloves that really break the habit of touching our faces. It is the unseeable mystery of air transmission that is causing the justifiable panic-level reaction in our business world. We must study, understand, mitigate, and control this air.
Bromage Excerpt 13: Interestingly, even though there were considerable interaction between workers on different floors of the building in elevators and the lobby, the outbreak was mostly limited to a single floor (ref). This highlights the importance of exposure and time in the spreading of SARS-CoV2.
JB: From what we heard of the disease, many of us, myself included, believed that being on an elevator would be very risky. But if all of this article’s logic is correct, then it is understandable that elevators do not expose you long enough to take in the necessary quantity of virus. If, if, if Bromage’s statements are fact, every high-rise building in the world would want to know this.
Bromage Excerpt 14: Choir: The community choir in Washington State. Even though people were aware of the virus and took steps to minimize transfer; e.g. they avoided the usual handshakes and hugs hello… A single asymptomatic carrier infected most of the people in attendance. The choir sang for 2 1/2 hours, inside an enclosed rehearsal hall which was roughly the size of a volleyball court. Over a period of 4 days, 45 of the 60 choir members developed symptoms, 2 died.
JB: Notice the critical conditions: Enclosed space, 2.5 hours. And the results of quantity X duration X proximity: 45 of the 60 choir members developed symptoms.
Bromage Excerpt 15: Commonality of outbreaks The reason to highlight these different outbreaks is to show you the commonality of outbreaks of COVID-19. All these infection events were indoors, with people closely-spaced…
JB: The formula is now…
Danger = Crowd Size X Duration X Proximity X Enclosure
Bromage Excerpt 16: Importantly, of the countries performing contact tracing properly, only a single outbreak has been reported from an outdoor environment (less than 0.3% of traced infections). (ref)
JB: Only 1 in 300 infections is from outdoors. No one wants to be the 1 (in 300) but remember that for COVID-19, only 1 in 5 infected people have serious symptoms. So only one in 1,500 of outdoor causation had serious symptoms. Approximately 1 in 4 with serious symptoms die, so I think this means 1 in 6,000 fatalities could be tracked to an outdoor infection.
Bromage Excerpt 17: Indoor spaces, with limited air exchange or recycled air and lots of people, are concerning from a transmission standpoint. We know that 60 people in a volleyball court-sized room (choir) results in massive infections.
JB: He’s saying that even recycled air is a risk. Retailers: open your windows and doors and put a fan at the front door. Facing in or out it probably does the same thing.
Bromage Excerpt 18: Social distancing rules are really to protect you with brief exposures or outdoor exposures. In these situations there is not enough time to achieve the infectious viral load when you are standing 6 feet apart or where wind and the infinite outdoor space for viral dilution reduces viral load.
JB: So the formula is now complete, and we’ll simplify crowd size to ‘people’:
Danger = People X Duration X Proximity X Enclosure X Air Stagnation
- If, if, if Dr. Bromage’s principles are facts, and you don’t sneeze/cough in each others’ face or linger in conversation, conducting business with a lot of airflow, whether indoor or outdoor is unlikely to produce a high risk of transmission from person to person.
- If, if, if Dr. Bromage’s principles are facts, and you don’t sneeze/cough in each others’ face or linger in conversation, conducting business outdoors is likely to be very low risk
I’ll let others comment on the relationship of masks to risk, but there is no disputing that masks make OTHERS feel safer.
Social events, even outdoor, cannot as easily be characterized for risk because people are naturally inclined to get too close to each other. I’ve seen it personally even among very conscientious people.
Bromage Excerpt 19: While I have focused on respiratory exposure here, please don’t forget surfaces. Those infected respiratory droplets land somewhere. Wash your hands often and stop touching your face!
JB: Neither the Bromage article nor my comments, draw conclusions about ‘touch transmission.’ But neither touch transmission, nor the fear of it, is causing the world’s economies to shut down. Face-to-face air transmission is what’s doing that!!! We can wash our purchases and learn to stop touching our faces, hard as it might be.
Conclusions
- Conduct business outside.
- Install visible fans.
- Open your doors and windows.
- Restaurants must replace face-to-face ordering with in-advance or paper, ballot-style slips.
- And don’t breath and sneeze on everyone else.
Experiments
Dr. Bromage, like others, explains that airplanes are known to have great ventilation systems, with filtration. So it occurs to me, we are missing an easy opportunity to save the airline industry, its employees, and all of the financial damage incurred by its shutdown:
We simply need to collect information from the people who have traveled by plane more than two weeks ago (longer than the incubation period) and establish their infection/hospitalization/fatality rate compared to the general public in both their cities of origin and destination.
If the rate is equal to or lower than the population as a whole, the air filtration on planes is strong, and it is relatively safe to fly. (Then, any advanced civilization would put those same air systems on trains and busses.) If the safety of air travel is confirmed, then Dr. Bromage’s theory, that infectivity is a function of people X duration X proximity X enclosure X air stagnation, must be ‘run up the flagpole’ and tested in disparate and regionally isolated milieus with experimental crowds of low-risk populations, where hospital loads are low. In three weeks we’ll know what environments and activities incur relatively low infectivity.
If “people X duration X proximity X enclosure X air stagnation” is the Bromage protocol, then let me leave you with this formula for reopening activities, the Bellis Protocol:
Re-socializing risk =
people X duration X proximity X enclosure X air stagnation
— — — — — divided by — — — — — -
open hospital beds x infection testing rate
In other words, if you aren’t doing any testing, your risk goes up; you have no idea how many asymptomatic people will rapidly infect highly susceptible people. As one example if the reports are correct, in Germany, at least one school tests students twice a week.
And if you have no empty hospital beds in an area, your risk also goes up, both as an individual who might need life-saving measures, and as a community that could quickly overrun its healthcare capacity.
