What does 56% look like?

December 26, 2020 8:51 PM

The new variant of coronavirus, which has now spread from the U.K. to several other natiions, is said to be "56% more contagious" than the original strain. What does this mean in terms of ordinary life?

While nothing is foolproof, we've all gotten used to a few mitigating practices which though certainly not eliminating one's chance of contracting the virus, do significantly lessen that chance. Things like a jogger suddenly passing too close to me on the street doesn't cause me to freak out anymore even if they exhale right next to me.. it just happens, and I don't like it, but figure it should probably be ok given that we're outside and there wasn't a "large" viral load in a moment of contact. And there is the constant sight of people with their masks below their noses being tolerated outside; going into a store masked and standing as far from others as possible but the occasional person not complying, etc etc. In general I've stopped freaking out at these transgressions while still doing my best to uphold the recommended guidelines.
But if something is 56% more contagious what does that mean in practical terms? Does it mean that instead of on average getting the virus in 15 minutes of contact, you'll on average get it in 6 1/2 minutes? Does it just mean that the infection transmission number of how many people each infected person infects changes by 56%, and if so, what does that mean for daily practices?
I know some people will rightly want to point out that we don't have control over such detailed aspects of spread in daily life, and that the best thing to do is stay home and wear a mask and so on. I agree with these points, and I am not looking for guarantees, I'm only looking for a statistics-based answer on what a 56% more infectious variant looks like vis-a-vis practices in daily life.

posted by ojocaliente to Health & Fitness (10 answers total)

Have you read this article from NPR?
posted by kinddieserzeit at 9:08 PM on December 26, 2020

Disregard the pseudoprecision inherent in a figure like 56%. "About 150% as contagious" or "50% more contagious" gives you the information you need.
posted by yclipse at 4:07 AM on December 27, 2020

I guess the theory behind the "56% more infectious" figure is that if you were to put 100 people through a mathematical model 20 of them were to become infected before- then the new strain would infect about 31. In this case the researchers are talking about the mathematical model they talk about in the (currently non-peer reviewed) paper they have published on the new strain here.

In practical terms, the percentage increase based on a mathematical model is of limited use in telling us how we might modify our behaviour - it is just a figure that says "this strain is more infectious; take care". The researchers have noted a correlation between places with sharp rises in infections - and places where the new mutant has been identified in tests, however. How might we take more care? I believe the answer is to just make sure we do whatever was working before: hand washing, social distancing, masks, vitamin D, ventilation, isolate and test.

In terms of exactly what might make the new strain more contagious: I don't think we know, but it might be reasonable to assume that the virus is better able to get infected in the upper airways to the extent that we need to breath in less of it to get infected. If we assume that then masks, social distance and ventilation and going to be the most important measures.
posted by rongorongo at 4:10 AM on December 27, 2020

There is not much that an individual can do for the reasons stated above. The percentages are modeled on the scale of large populations.

The main impact will probably be on ICU bed contention, and hence the timing of the various lockdowns and etc. that the public health departments mandate. I would expect that if this variant becomes a dominant strain, then lockdowns and other measures will be more frequent and last longer.

Areas without measures will see higher death rates due to lack of hospital beds or other healthcare resources.
posted by pdoege at 12:08 PM on December 27, 2020

Just want to agree that a number like 56% gives a false sense or precision. There's a big amount of uncertainty on that. What it means that there might be a strain of virus that spreads 1.5 times as fast as before. 1.5 times the rate of spread means people have 2/3 the time to react to outbreaks and people can have 2/3 the contact they were having before an outbreak becomes uncontrolled and grows exponentially. A two week response time will need to be 10 days now to limit spread to the same degree. Two thirds as many people can ignore the advice and regulations before things get out of hand. Maybe even fewer than that, because some essential services and contact need to happen no matter what.

Another consequence is that, since it grows faster, it will very quickly become the dominant strain. Exponential growth rates do not average out. The thing with the biggest growth rate will always win in the end. Unless the area you are in is keeping 100% of outside coronavirus infections out, the faster growing variant will become the main variant in your area in less time than you would like.

The early models that said you need to lock down hard the moment you notice that there's an exponential growth in cases already were assuming a lower growth rate than the virus turned out to have. The virus was well past the threshold where "lockdown and limit contact as much as possible" is the only course of action that will keep hospitals from being overwhelmed. A faster growing strain only adds a few more exclamation points after that advice.

If you are doing everything you can: not visiting anyone outside your home, only going grocery shopping every week or two and wearing a mask when you do, then you are fine. You are doing your part. You are doing all you can do. You aren't going to be the one responsible for spreading the virus around. You are fine.

Just don't cheat. Don't give in to thinking "just this one time will be fine." And if you do, well, definitely keep it to that one time, because what's really risky is slipping into believing that you're being more diligent than you actually are.

Other than that, support politicians that are taking things seriously in your area. Tell them you do not want them to give into the temptation to open things up just a little bit more because maybe it will be OK. It will not be OK. The math behind exponential growth is not forgiving. The difference between cases growing steady and an uncontrolled outbreak is the difference between 1 and any number number greater than 1, no matter how small that amount is. It is literally the narrowest difference imaginable. It is for all intents and purposes nothing. Unless the number active cases, hospitalizations, and death rate are all trending down so much that is is absolutely unambiguous, no one should even be thinking about loosening regulations.
posted by Zalzidrax at 1:08 PM on December 27, 2020

Tell them you do not want them to give into the temptation to open things up just a little bit more because maybe it will be OK.

Yeah, in the US that's categorically not going to happen because if businesses close, everyone slow starves and gets evicted and they aren't going to get a government bailout.

Unfortunately, you can only take care of you. Nobody else is going to take care of you. Protect yourself as much as you can by staying in, hope for the best, wait for a vaccine.
posted by jenfullmoon at 4:43 PM on December 27, 2020

Here's an answer that is simplistic, but might give a useful perspective.

All else being equal, your risk of getting infected in a brief encounter is proportional to two factors: the contagiousness and the likelihood that the other person is infected. The first factor has a mystique to it since we're used to thinking of it as constant (or, more likely, not thinking of it). But the second factor has always been in flux, and in the US is currently much more than 56% higher than it was at the summer peak.

All else may not be equal. But until we know more about the new strain, it's reasonable to suppose that a 56% increase in contagiousness affects your individual danger level in a given encounter just like a 56% increase in cases in your community -- something you've probably already had to decide more than once how to adjust to.
posted by aws17576 at 7:54 PM on December 27, 2020

A few things about the spread of the variant: as others have explained, a more infectious strain will tend to dominate others globally because that is the one that people will pick up and pass on. A higher infection rate also implies that - in the absence of other preventative measures - we will rush towards the point of herd immunity more rapidly than we would do otherwise: a shorter but more brutal pandemic. Finally the % infected figure we will need to achieve herd immunity will be higher than it it would have been otherwise - because a more infectious strain can push its way harder through an environment containing a given percentage of immune people. So we might need 80% rather than 70% for herd immunity to act as an effective fire-break. Vaccines do look like they are arriving just in time to help mitigate these trends.

For more, I'd recommend Dr John Campbell's videos - he has been providing daily updates on the pandemic for nearly a year.
posted by rongorongo at 11:47 PM on December 27, 2020

It means that a range of levels of lockdown that would result in a retransmission (R) rate of less than 1 (i.e., virus being extinguished) for the old variant will result in a retransmission rate of greater than 1 (i.e., exponential growth of infections) for the new variant. It means that stricter lockdown will be required to control the spread of the new variant, and at the same level of lockdown the new variant will spread much faster. This is a major public health problem.
posted by heatherlogan at 9:26 AM on December 28, 2020

Stephen Reicher - member of the Independent SAGE committee that advises the UK government- offers some specific policy recommendations for coping with the new variant.
posted by rongorongo at 3:05 PM on December 28, 2020