Coughing and germs

[redbird]

The last few years, there's been a lot of encouragement to cough into your elbow instead of covering your mouth with your hand or a tissue. It sounds good, but does it help?

A team in Edmonton compared different "cough etiquette" maneuvers to see whether they would prevent the spread of viruses. Covering your mouth with both hands, a tissue, a clothed elbow, or the usual , including covering your mouth with both hands, a tissue, a clothed elbow, or a surgical mask are all equally ineffective.

The basic problem is that aerosol drops are too small to be blocked by any of those things.

So that leaves us with vaccination, hand-washing, and staying home when sick, which of course many people can't afford to do. (And that person on the bus who is coughing or sneezing might be reacting to an allergy, which is not contagious.)

As a side note, you have read every scientific study that supports coughing into your elbow. Really. There aren't any.

After noting the problem, the authors encourage research to find evidence-based procedures that do block the transmission of respiratory disease. In the meantime, I think I'm going to start carrying hand sanitizer. If you're in the Northern Hemisphere and haven't already gotten a flu vaccine, they're widely available in the U.S. and Canada (I haven't checked on other countries). If you're in the U.S. and have health insurance, it's probably covered. If you're in Canada, the categories of people who can get it free vary by province.

Conclusions

All the assessed cough etiquette maneuvers, performed as recommended, do not block droplets expelled as aerosol when coughing. This aerosol can penetrate profound levels of the respiratory system. Practicing these assessed primary respiratory hygiene/cough etiquette maneuvers would still permit direct, indirect, and/or airborne transmission and spread of IRD, such as influenza and Tuberculosis. All the assessed cough etiquette maneuvers, as recommended, do not fully interrupt the chain of transmission of IRD. This knowledge urges us all to critically review recommended CE and to search for new evidence-based procedures that effectively disrupt the transmission of respiratory pathogens. Interrupting the chain of transmission of IRD will optimize the protection of first responders, paramedics, nurses, and doctors working in triage sites, emergency rooms, intensive care units, and the general public against cough-droplet-spread diseases.

[Via the Science-Based Medicine blog, tucked in near the end of a piece about osteopathic manipulation.]

Comments

[kaberett]

Where of course the reason I cough/sneeze into my elbow has nothing to do with caring about disease vectors and everything to do with wanting to minimise the amount of grot I cover my gloves in... :-)

[redbird]

Sure, and there's no reason not to do it that way: using your hands isn't better than your elbow, either. I will probably keep sneezing into my elbow, just to avoid feeling like I have to wash my hands right away.

[liv]

Really interesting piece of research, thanks for passing that on. I tend to sneeze into my elbow because, well, I'm a lab scientist and I hang out with doctors, so it would make me look really weird to go against the local culture. But it's definitely good to have evidence for these things and not just assumptions.

[ironed_orchid]

I try to cough or sneeze into my elbow in public places so that I don't go around touching doors or holding onto poles or rails on the train with a slimy hand.

[aedifica]

Yes; I didn't think the point was that it stopped the germs from floating around, but that one wasn't putting them on one's hand to spread them further.

[striped]

This is really interesting!

I guess turning to cough away from nearby people, or preferably moving a distance away from people, could maybe be effective to some degree. Although there are plenty of situations where you can't do this, like on the bus where there are people all around you.

[conuly]

Wait, wait, wait - does this apply to sneezes as well? Because I just spent the better part of three months trying to teach Ana to cover her mouth when she sneezes, and I would hate to think I did so under false pretenses! (We had just been reminding her after the fact, but after she sneezed directly on my plate I blew up at her and it came out she had no idea what signals her body made before she sneezed. Once that was sorted out she had no problem.)

[redbird]

I don't know whether it applies to sneezes: the paper specifically tested coughing. (It's open access, and written at a level that I, a non-biologist, could understand.)

I suspect it's worth her covering her mouth when she sneezes if only for social reasons: if most people believe that it stops disease from spreading, they'll think she should do it. But I suspect it doesn't matter whether she uses a tissue or her elbow.

[r-ness.livejournal.com]

As a side note, you have read every scientific study that supports coughing into your elbow. Really. There aren't any.

Well then! Thanks for that.

The team in Edmonton should test some N95 protective masks that are now very popular in China. People wear them to protect themselves on days when the PM 2.5 level becomes dangerously high. Ordinary surgical masks do not help against this any more than they help against coughs. From http://www.greenpeace.org/eastasia/campaigns/air-pollution/problems/coal-hard-truth-air-pollution/: "One strap paper masks and ordinary surgical masks has no effect on PM2.5 prevention."

The 2.5 in PM 2.5 refers to micrometers, so if I'm reading the paper correctly the mask should protect against transmission in three of the six categories they grouped droplets into: "These averages were grouped into six (6) categories according to droplet size: a) < 0.5 μm, b) 0.5 to 1 μm, c) >1.0 to 2.5 μm, d) >2.5 to 10 μm, e) >10 to 100 μm and f) >100 μm."

On the other hand, the masks are generally designed to keep things out. I suspect the pressure generated by a cough might blow the mask off far enough to break the tight seal you're supposed to keep between the mask and your face.

Further research warranted, etc.

[redbird]

The "masks don't help" is based partly on French and German research.

I suspect, and hope, that those PM 2.5 masks are helping the wearers. But my doctor's office is in a hospital that has signs saying that if you have flu symptoms and are an employee or visitor, turn around and go home. If you are there to be treated that day, go directly to reception and ask them for a mask at check-in. That's either based on believing that the masks reduce the spread of germs, or a way of telling sick people to identify themselves so other people can keep their distance. (Though they're unlikely to say the latter.)

[r-ness.livejournal.com]

I think there is also Chinese research that ordinary surgical masks are worthless against particles that small.

That having been said, the air pollution is probably a bigger problem than the germs. I imagine that the two together have some really bad synergistic effects.

[beckyc.livejournal.com]

That's interesting (and a bit disturbing) to know!

Flu shots are cheap and usually readily available in the UK (free for "at risk" groups or if GP surgery have spare; many employers supply them free, or you can spend about ten pounds at a pharmacy or major supermarket)

[browngirl.livejournal.com]

*makes a note*

[amaebi.livejournal.com]

No doubt it works through The Juju.

And it keeps off both dragons and lynchings quite well.

[gerisullivan.livejournal.com]

I thought the idea behind using the elbow for coughs and sneezes was to reduce the amount of contagions on hands, which then touch all sorts of things, not that the elbow blocked any more of the droplets than hands, tissues (held by hands) or anything else.

If I understand the discussion correctly, the researchers would agree:

"While global health authorities and agencies do not recommend covering the mouth/nose using bare hands when coughing, this procedure was included in our study for comparison of droplets released into the environment when using hands. We fully agree that when using the hands to cover the cough, respiratory pathogens could be transmitted to other individuals if contact precautions are not followed."

I agree with your comment about vaccination, hand-washing, and staying home when sick.

[adrian-turtle.livejournal.com]

Wait! Who says the purpose of coughing into your elbow or a tissue is to reduce airborne droplets? I always thought it was to reduce droplet transfer via hands. If you don't cough directly into your hands, you don't spread as much contagion to local doorknobs or the hands of your neighbors. And if you don't couch directly onto surfaces your neighbors touch (whether we're talking about doorknobs or your hands or the support poles in the subway), they won't spread those droplets to their own faces.

Likewise, paper face masks can't filter viruses, but they make people touch their faces MUCH less often. Nose-1 to hand-1 to hand-2 to nose-2 is way more efficient than nose-1 to air to nose-2, unless the noses are very close together.

[redbird]

It seems worth noting, though, that none of these will actually stop you from spreading germs by coughing or sneezing (she typed, ruefully, with a cold). Similarly, filter masks by themselves don't reduce the spread of respiratory infections within a household; masks plus handwashing do.

[beginning.livejournal.com]

Well, that's gross.