Will the lockdown hurt your immune system?

In my last post, I called out pro-shutdown hoaxers who think that misinformation is okay so long as it gets people to do what they want them to do. In this post, I'd like to call out misinformation circulating on the anti-shutdown side. In particular, I'm thinking of one video that has made a large splash, in which two physicians (I'm not in a position to verify whether they are what they claim) make a bunch of statements about immunology and microbiology, and then say how they think those ideas apply to the pandemic - specifically the lockdowns.

I won't link to it, since it's being taken down wherever it's posted anyway, but I do want to go over why the things they say sound true but ultimately are not. Let's boil down a few of their claims so we can refute them one by one. I'll highlight the claims in yellow in the paraphrased statements below, and put the true statements in orange:

  1. Commensal bacteria and viruses are everywhere, your immune system needs these to function properly; washing your hands a bunch (sterility) robs you of commensals and is therefore bad for your general health.
  2. Pathogenic bacteria and viruses are also everywhere, your immune system needs these to function properly; keeping people from sharing pathogens weakens their immune systems.
  3. Because of this, when the lockdowns are lifted people will be more susceptible to infections.

Each of these are based on ideas from immunology that are true, but they extend them to situations where they are no longer true. Kind of like saying, "If you add up the angles in a triangle it will always come out to 180 degrees; here's a rectangle that has a bunch of angles, so we know they'll all add up to 180 degrees." There's a subtle shift halfway through between established theory and a false claim.

These aren't direct quotes, as I said I've lost the video where I originally saw it because it got taken down, but they're a fair representation of the claims made. Let's start with the first point above:

Does excessive hand washing rob you of commensals?

Commensal bacterial and viruses are all over the place. This is indeed one of the benefits babies get from going around sticking everything in their mouths. A friend in grad school went to a talk at an immunology conference called, "let them eat dirt", about the benefits of exposing young children to environmental bacterial and viruses. You get exposed to them and they live on your skin and in your lungs, gut, mouth, etc. However, commensals are also found in your back yard. So if you're sterilizing the counter top so the kids don't get sick from the raw chicken you were cutting up that's still a good thing to do. Just send them out into the back yard to play and they'll be fine. Better yet, if you have a dog let the dog lick them in the face. Dogs pick up lots of commensals, and they're happy to spread the wealth. There's evidence to suggest children who grow up with a dog in the house are less likely to develop autoimmune disorders, and we think this is the reason why.

None of this should be prevented by social distancing, since the most important source of commensals is from the environment you interact with every day, not the chance encounter at the grocery store.

In addition, there's an implied claim that the shutdowns will result in a decreased amount of commensals in your body. The idea seems to be that if you don't continually supply people with new sources of commensals the ones they have will eventually go away. This isn't how it works. There's a pound of bacteria in your gut, and they get to start eating your food before you do. So long as you keep feeding them they'll stay in there. If you decided to fast for a few days they'd sit around, waiting for you to eat again, then grow back out to where they were.

Crucially, which commensals are dominant is much less dependent on whether you wiped the counter down with lysol, and much more dependent on what you ate for lunch. Here's a practical example: there are certain bacteria that are really good at feeding off of certain molecules in beans, so when you eat a big pot of chili those bacteria will grow faster than the others. These bacteria also produce lots of methane as a digestive byproduct, so you'll have a lot of embarrassing gas while the bacteria eat the beans. Once the beans go away, the bean-eating bacteria will die back down to low levels. There they will stay until Taco Tuesday comes around again. But even if you don't have beans for six months - or even a few years - those bean-eating bacteria will stick around waiting for their chance. Your commensals will be fine throughout the shutdown, even if they extend it through next year.

Does social distancing weaken your immune system?

It's gratifying to see concepts that were somewhat new to immunology a couple decades ago finally making their way into the public's consciousness. It's less gratifying when they're applied to every situation in a way that demonstrates the concept is almost entirely misunderstood by the public at large. The idea that's mutilated in this instance is called Hygiene Hypothesis. The way people seem to think HH works is that all pathogens, everywhere, boost your immune system - so if you don't get constant exposure to pathogens your immune system will get weaker, like a muscle. But that's not how the HH works, and it's not how the immune system works. The HH doesn't care about your exposure to all pathogens, just specific kinds of pathogens - mostly parasites and a few kinds of mycobacteria, etc. I don't expect the general public to be able to parse the nuance here, but let's just say that SARS-CoV-2 isn't going to prevent asthma or whatever, which is what the HH is pointing at.

Meanwhile, it's wrong to think of the immune system like it's a muscle, needing constant exercise. A better analogy is to think of it like it's a brain. The distinction is important. For a muscle, you can lift lots of weights in a gym and then when you help your friend move it's much easier to pick up the furniture, even if it's something you'd never even seen before. (If I knew you owned a baby grand piano in the basement I would never have agreed to this!) Likewise, if you're already six grocery bags from the car, it may be difficult to grab the other six and make the whole thing in one trip. But the immune system isn't like this. It's perfectly capable of fighting off multiple infections at the same time. You can have a fungal infection, a sunburn, indigestion, and the flu and the infection in one body system isn't going to 'pull resources' significantly way from the other systems.

The brain analogy is much more apt. If you learned a bunch of facts about the American Revolutionary War that doesn't mean you know anything about the Mexican Revolution. Your body doesn't get stronger against measles because you had chicken pox. Every infection is treated in its own way. This means you can get infected with measles, then a couple days later with chicken pox, and your immune system will fight off both infections at the same time, independently developing antibodies against both viruses.

So what of social distancing? Will it weaken your immune response? Obviously getting sick from pathogen A isn't going to prevent you from getting sick from pathogen B, so the only argument would be that during lockdown if you don't get sick from something that you get sick from later all you did was delay an inevitable infection. And some infections will of course be skipped entirely, which can only be a good thing for your health.

Will the lockdown make people more susceptible after things open up again?

You'll forget facts you learned back in school if you don't get exposed to them again from time to time. Your immune system is the same way, but it's much better at remembering things than your brain. If you're exposed to a pathogen you'll keep the antibodies around for a lot longer than a few months. You keep them for about a decade or more (it depends on the kind of infection/exposure, so some things will be longer than ten years, but a decade is a good rule of thumb). This is why they recommend you get your childhood vaccinations renewed when you get into your 20's, because by then your immune system is much less prepared for something it hasn't seen in a few decades. You still keep some antibody-producing cells around, so it's not a total loss - you'll still get some protection if you get exposed again. It's just that your residual immunity after all that time might not be enough to keep you from getting sick without a new exposure.

Now, if a lockdown was extended for a decade or more, might you become more susceptible to lots of different pathogens you didn't get exposed to during the ten years you were locked in your house? Sure, maybe. That would at least be a valid concern. But over a couple of months, or even a couple of years it's not a valid concern. Your immune system isn't going to forget everything it knows just because you stayed home over the winter - and that's a good thing!

As I talked about in my last post, this pandemic is not nearly as bad as many historical pandemics. Epidemiologists have been saying for years that another pandemic like earlier ones that changed the course of history could happen again at any time. It could even happen during the COVID-19 pandemic, though if it did that would just be a coincidence. If something came along with the ability to kill five percent of the population - or more, there's historical precedent for fatality rates much higher than one in twenty people - we'd want to institute some serious lockdowns. And as I pointed out in my last post, we now have strong evidence that lockdowns would help. There's nothing about a lockdown that's inherently detrimental to the immune system. After all, our ancient ancestors often lived in groups of 20 or less, stayed away from non-existent large gatherings, and sometimes went for months in total isolation.

The question isn't whether the idea of a lockdown is bad for your immune system, per se. The question is whether this particular virus merits a lockdown. You can make coherent arguments about the merits of this lockdown, but the arguments about whether the idea of a lockdown in general is harmful to the immune system are not grounded in immunology or microbiology.

Comments

Popular posts from this blog

Nutrition Graph: Cereal Comparisons

Covid-19: Epidemiology is useful

Reverse Engineering Life