How coronavirus spreads and why homemade masks are suddenly the rage
(Rick Egan | The Salt Lake Tribune) Missionaries from The Church of Jesus Christ of Latter Day Saints wear face masks as they walk down West Temple, Thursday, April 9, 2020
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You’re (probably) not a doctor. You (almost certainly) don’t even play one on TV.
But for the sake of this column, I want you to pretend you’re not just any doctor, but the one in charge of something like the World Health Organization (WHO) or the U.S. Centers for Disease Control and Prevention (CDC). You’re the one making recommendations about how the public should act in the face of COVID-19.
You have an enormous amount of power. What are you going to tell them? How are you going to stop this disease?
You start with the basics: how diseases spread. Here are the top five
1. Direct contact: An infected person hugs, kisses, shakes hands, etc. with another person.
2. Respiratory droplets: An infected person sneezes, coughs, or even talks, and out come droplets containing pathogens. Those droplets immediately land on someone.
3. Airborne transmission: An infected person sneezes, coughs or talks, and the droplets remain suspended in air. A new person comes along and breathes them in.
4. Fomite transmission: An infected person sneezes, coughs or touches something. Later, a new person comes along and touches that thing, then touches their face. (“Fomite” — one of the most unnecessary pieces of jargon I’ve ever come across — is the word that medical professionals use when referring to a thing that might be infected. “Thing” would have worked fine.)
5. Fecal-oral transmission: The gross one. The disease is in an infected person’s feces, then feces particles end up on a surface. Someone touches the surface, then touches their mouth, nose or eyes.
Well, the first few recommendations are easy, right? You tell people to stop shaking hands
. You teach people how to sneeze and cough into their elbow and not on someone. You tell people to stop touching their faces. And that they should wash their hands consistently and thoroughly.
But wait! What does consistently and thoroughly mean? There’s no doubt that hand washing is really useful. But across a review of 300
hand-washing experiments, the differences in results are striking. Some hand-washing strategies remove 90% of virus load on the hands, some remove 99%, some 99.9%, and so on — but the results are pretty inconsistent from study to study. It’s a hard thing to measure. The good news is that there’s widespread agreement that plain soap works really well on coronaviruses.
You also know that many people
don’t wash their hands. So you try to strike a balance between Howard Hughes-esque hours of hand washing and what most people are likely to actually perform. In the end, the CDC says you should wash your hands for 20 seconds
. The WHO recommends 40 to 60 seconds
. Who’s right? There isn’t a right or wrong. And neither strategy is going to leave your hands 100% virus free, anyway.
Hand washing was one of the easy recommendations, and even it turned out not to be so simple. It was your warmup.
Let’s skip ahead to a much more complicated task, a topic of real-life debate over the past month. Should you recommend that everyday people wear masks?
I have bad news: The information you have available is still evolving on this one. And it certainly wasn’t very robust two months ago.
First, the studies available about masks preventing people from getting a disease are frustratingly all over the map: some say masks really help, some say they don’t do anything, and at least one has even claimed they increase transmission as people fiddle with their mask and touch their face more.
This Forbes article has a good breakdown
, but in summary: One 2015 review of nine studies
found that real-life use of surgical masks did not reduce infections compared to no masks — except for the study that said they did. One review of studies
said masks helped during SARS (a type of coronavirus), one review said
they didn’t during pandemic flu. There are dozens of other studies, and they are not any more authoritative.
Given that there is a mask shortage and that the research was uneven, many public health officials didn’t immediately recommend that everyone wear one. The U.S. surgeon general, for example, begged people not to buy masks
in a Feb. 29 tweet, calling them “not effective in preventing general public from catching #coronavirus.” Save the masks for the doctors, the thinking goes.
There is general agreement that masks are effective at one important thing, though — they help preventing infected people from spreading the disease by blocking a large percentage of droplets containing the virus at the source. But many thought this could also be efficiently handled by telling symptomatic people to stay home.
Previous coronavirus outbreaks, like SARS and MERS, were transmitted less frequently or even not at all
from asymptomatic individuals. It took time for people to realize that COVID-19 was different. Back on Jan. 30, a new study in the New England Journal of Medicine
documented asymptomatic infection in China. But many criticized the study, because at least one person labeled as asymptomatic probably had at least mild symptoms.
Real life, though, continued to show clear cases of asymptomatic transmission via the air. Take the Skagit Valley Chorale practice
in Washington, in which 60 asymptomatic singers showed up with hand sanitizer in tow on March 10. Later, 45 of them tested positive. That certainly points to respiratory and airborne infection being a major method of transmission.
And epidemiologists have been able to trace this further. Here are three clusters of spread
in Singapore, as represented by a graph made by Channel News Asia:
Channel News Asia (https://www.channelnewsasia.com/news/singapore/covid-19-new-clusters-ce-la-vi-singapore-cricket-club-apr-3-12606542)
These are the kinds of clusters that COVID-19 epidemiologists keep finding everywhere: groups of people who are in the same location for an extended period of time who end up passing the disease to one another. The people in Hero’s Bar, or the Dover Court School, or the Singapore Cricket Club didn’t all shake hands. They could have touched some common surfaces, like a door handle, but it’s relatively unlikely that they all got it from the same object.
The science began to show to what extent asymptomatic transmission through droplets was possible. A March 17 study
found that the virus can live suspended in midair for about a half hour. And a March 26 study
said that sneezes can shoot droplets containing pathogens about 23-27 feet. Even then, I should note that there are all sorts of relevant questions unanswered: how much of the virus do you need to accumulate before you’re likely to become sick? How likely is that amount to still be in the air 25 feet away or 30 minutes later? We don’t know.
Some especially stubborn folks didn’t cave on this issue until a CDC study released on April 1
made clear just how frequently COVID-19 can be transmitted by asymptomatic individuals — and for up to 3 days before they develop symptoms.
All of these studies and experiences have coalesced into a new recommendation
from the CDC: Yep, people should wear masks.
Masks aren’t a replacement for social distancing — even the most optimistic look at the subject finds masks alone reduce the contagion significantly less than staying home.
When people do occasionally have to venture outside, they should wear one. Given the shortage, people are going to have to make their own. The best resource I could find for how effective these masks are is from researcher Paddy Robertson
, who conducts various experiments on the masks and reports his findings. For example, here are the results showing how well masks made of different materials work to stop 0.02 micron particles. This coronavirus has particles that range in size from 0.06 to 0.14 microns.
Smart Air Filters (https://smartairfilters.com/en/blog/best-materials-make-diy-face-mask-virus/)
As you can see, even leaky masks make a difference when it comes to particles smaller than the coronavirus. (One note: Many vacuum manufacturers do not recommend
using their bags as masks.)
It took time for those in charge to make this recommendation. If, under your regime as Head Doctor, you would have made this move faster, I’d understand that. But the issues here are difficult, and as much as you’d like the epidemiological science to be clear, sometimes it’s just not.
If anything, we have learned one important lesson: it’s easier to stay at home and watch the doctors on TV than to be one.
Andy Larsen is a Tribune sports reporter who covers the Utah Jazz. During this crisis, he has been assigned to dig into the numbers surrounding the coronavirus. You can reach Andy at email@example.com or on Twitter at @andyblarsen.