New NEJM Article: COVID-19 Disease Transmission Is Close Contact

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Much of what we know about COVID-19, if it were put in a trial format in front of a jury, would be in the category of weak circumstantial evidence. Much of that has to do with the fact that high-level controlled science takes a long time to plan, recruit, execute, write-up, and then get published. However, we’re just now starting to see our first studies published that scientists would consider non-circumstantial. Let’s dig into a nice study on Marine recruits.

How Is the Virus Transmitted?

This is the multi-trillion dollar question, right? If this virus can be transmitted by walking by someone in the park, we need one set of rules to prevent transmission. If it can be transmitted mostly by close contacts living together, we need another set of totally different rules. Given that those rules will determine whether the world economy is shut down or can limp along, this is a very big deal.

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What Do We Know?

Regrettably, what we know is in that category of “circumstantial” evidence. In a trial, this would be the weakest type that juries are often told to give little weight. For example, most of our data on how the SARS-Cov-2 virus is transmitted comes from what’s called “community contact tracing”. What’s that?

Community contact tracing means that if a person gets an infectious disease, you ask that person to list all of the people that they came in contact with over the past two weeks. Think about that for a minute. Could you tell me every person who you might have had contact with over the past few weeks? How about that Target run for toilet paper? How many people did you come close to or share a surface with? Or that food you picked up at the local restaurant? Did someone bump you? Who touched the bag you picked up before you picked it up? Was the guy in line behind you wearing a mask and closer than 6 feet? As you can see, there would be a very wide margin for error when using community contact tracing to study disease transmission.

The New Study-COVID-19 in The Military

If there ever was a place where every aspect of your life is strictly controlled 24-7 it would be in the world of marine recruits. Someone else determines when you eat, where you eat, where you sleep, when you wake up and go to bed, how your area is cleaned, the clothes you wear and how, etc… While for recruits this is a nightmare writ large, for scientists studying COVID it’s nirvana. Why? To do good science you need strict controls.

The new research looked at 1,848 recruits who were part of a highly controlled experiment (1). How controlled? This is from the paper:

“All recruits wore double-layered cloth masks at all times indoors and outdoors, except when sleeping or eating; practiced social distancing of at least 6 feet; were not allowed to leave campus; did not have access to personal electronics and other items that might contribute to surface transmission; and routinely washed their hands. They slept in double-occupancy rooms with sinks, ate in shared dining facilities, and used shared bathrooms. All recruits cleaned their rooms daily, sanitized bathrooms after each use with bleach wipes, and ate preplated meals in a dining hall that was cleaned with bleach after each platoon had eaten. Most instruction and exercises were conducted outdoors. All movement of recruits was supervised, and unidirectional flow was implemented, with designated building entry and exit points to minimize contact among persons. All recruits, regardless of participation in the study, underwent daily temperature and symptom screening. Six instructors who were assigned to each platoon worked in 8-hour shifts and enforced the quarantine measures. If recruits reported any signs or symptoms consistent with Covid-19, they reported to sick call, underwent rapid qPCR testing for SARS-CoV-2, and were placed in isolation pending the results of testing.”

Meaning every aspect of life, the universe, and everything was controlled here as much as anyone can control what another human being does or doesn’t do. In addition, unlike an experiment with volunteers, the instructors, for all intents and purposes, have unprecedented powers to enforce everything, Meaning, step out of line and you get to spend time in the brig.

The study also used sophisticated viral genome sequencing to track how specific viral strains spread among the recruits. Hence, if there ever was a place where contact tracing could be done right with very little wiggle room for error, this was it.  Hence, we should give tremendous weight to what these authors found.

Who Got the Disease?

Only recruits who shared rooms and were part of the same platoon spread the disease. In particular, even recruits who were close by and shared a bathroom with those infected didn’t get infected. Hence, only those who lived two to a room and who worked closely together got this virus.

So while living in an ideal COVID-19 world where all precautions were taken, nobody got the virus through the air while walking past someone. Nobody got the virus from a food worker. Nobody got the virus by using the same bathroom.

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This Is a Close Contact Disease Transmission Scenario with Superspreader Events

Looking at the real data here, the stuff that’s actually high quality, this disease is spread by close contacts. That means people living or working in close proximity to each other. This is why we see this disease spread quickly in immigrant communities who often live in high occupancy settings or work side by side on product lines.

This disease can also be spread through rare “super spreader” events. That means that one person, for reasons we don’t understand, can spread this to 6 people or more. Maybe they have more viral shedding? Maybe they are huggers? We don’t know.

What Does This Mean for Me?

First, breathe. Second, COVID-19 is very unlikely to be transmitted because someone walks too closely to you. You also likely can’t pick it up by using a public restroom or ordering food. Wear your mask where they tell you to do so, follow social distancing, and wash your hands. If you have someone in your home who you live in close contact with who is sick or positive, then get tested.

The upshot? This military recruit study is about as good as it gets, which is why it was published in the New England Journal. Meaning, it’s rare to find a real-world study where this number of variables was strictly controlled. I’m very thankful we’re actually starting to get some real science published!



(1) Letizia AG, Ramos I, Obla A, Goforth C, Weir DL, Ge Y, Bamman MM, Dutta J, Ellis E, Estrella L, George MC, Gonzalez-Reiche AS, Graham WD, van de Guchte A, Gutierrez R, Jones F, Kalomoiri A, Lizewski R, Lizewski S, Marayag J, Marjanovic N, Millar EV, Nair VD, Nudelman G, Nunez E, Pike BL, Porter C, Regeimbal J, Rirak S, Santa Ana E, Sealfon RSG, Sebra R, Simons MP, Soares-Schanoski A, Sugiharto V, Termini M, Vangeti S, Williams C, Troyanskaya OG, van Bakel H, Sealfon SC. SARS-CoV-2 Transmission among Marine Recruits during Quarantine. N Engl J Med. 2020 Nov 11. doi: 10.1056/NEJMoa2029717. Epub ahead of print. PMID: 33176093.

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3 thoughts on “New NEJM Article: COVID-19 Disease Transmission Is Close Contact

  1. Sam

    A Portuguese appeals court has ruled that PCR tests are unreliable and that it is unlawful to quarantine people based solely on a PCR test. The court stated, the test’s reliability depends on the number of cycles used and the viral load present. Citing Jaafar et al. 2020, the court concludes that: “if someone is tested by PCR as positive when a threshold of 35 cycles or higher is used (as is the rule in most laboratories in Europe and the US), the probability that said person is infected is less than 3%, and the probability that said result is a false positive is 97%.”

  2. schutzhund

    Ok, so how and/or where did the original carrier get the virus? They were not tested before the trial run?

    1. Chris Centeno, MD Post author

      That would have been through animal to human transmission based on the current theory. This paper looks at human to human transmission.

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