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Homework Report: What Did the CDC Recommend About Cleaning Surfaces Last Year?

Last week I had lunch with my friend DF and the conversation turned to the general subject of the CDC. Stripped to its basics, the question was: Are they idiots? Or are they just doing their best to follow the science at a time when the science is evolving quickly?

The specific subject we chose as a test case was the CDC's advice about disinfecting surfaces in March 2020. I agreed to look into this, which turns out to be a little tricky. I need to go back in time and figure out (a) what the CDC's advice was at the time, and (b) what the best science said at the time.

So here we go. As near as I can tell, the CDC's advice in early March was pretty straightforward: You should clean high-touch surfaces daily, but the risk of catching COVID-19 from surface contact is very low. Here's a typical media report from March 12:

Coronavirus mostly spreads from person to person within about six feet, according to the CDC.

The CDC said it hasn’t seen transmission of this virus from surfaces to people....The CDC said the best thing to do is clean visibly dirty surfaces in your home and then disinfect them.

The problem is that a few days later a study was released that said the coronavirus was stable on some surfaces for quite a long time:

The scientists found that severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was detectable in aerosols for up to three hours, up to four hours on copper, up to 24 hours on cardboard and up to two to three days on plastic and stainless steel.

This did not change the CDC's advice, but it did get a huge amount of media attention. People started fretting about disinfecting every surface they touched, leaving groceries in the garage for several hours after you brought them home, and quarantining mail for days. But here's Dr. Fauci in mid-March at a CNN town hall:

I think if you start thinking about money and mail and things like that, you can almost sort of immobilize yourself, which I don’t think is a good idea.

And here he is in late March:

“I don’t think we need to get completely obsessed about packages that come in because those types of surfaces — the virus might live there for a very short time," Fauci explained. “But people say ‘Should I get a package from a grocery store that says made in China?’ I wouldn’t worry about that. That’s not the issue.”

The CDC itself was pretty consistent throughout all of this: There was little danger of contracting COVID-19 from groceries or packages or from food. You should clean things like doorknobs frequently, but that's probably enough. Mainly, you should practice social distancing and wear a mask. Much of this got drowned out by media coverage of the coronavirus surviving for days on common surfaces, but you can't blame that on the CDC. They pushed back on that and maintained their more moderate advice.

But there's one more thing. DF was especially dismayed by the closure of outdoor playgrounds even though there was evidence that sunlight kills the coronavirus very quickly. And that's true. Here's a media report from late April:

"Our most striking observation to date is the powerful effect that solar light appears to have on killing the virus, both surfaces and in the air," he said.

....The virus's half-life—the time taken for it to reduce to half its amount—was 18 hours when the temperature was 70 to 75 degrees Fahrenheit (21 to 24 degrees Celsius) with 20 percent humidity on a non-porous surface.... In the presence of sunlight, this dropped to just one and a half minutes.

But there was also this:

Half the virus may be killed in as little as two minutes if it’s on a surface exposed to sunlight and high humidity at room temperature.... Under drier, shady conditions, the virus’s half-life is far greater — around 18 hours.

And this:

“It doesn’t make it safe to go out to the beach because the time it takes for the sun to kill the virus is exceptionally long,” Armani said.

A coronavirus’ outer layer weakens as the temperature rises, Armani said....But the sun won’t make much difference in spots where shade or clouds reduce the optical intensity of sunlight. Nor will sunshine prevent the virus from spreading from person to person through droplets of saliva or mucus in the air.

Karin Michels, chair of the epidemiology department at UCLA’s Fielding School of Public Health, said there was “no good data” to support the idea that the UV in sunlight would make any difference in the coronavirus infection rate.

In any case, I couldn't find any evidence that the CDC said anything about playgrounds one way or another. The National Recreation and Park Association advised closing playgrounds, and many local communities followed that advice. Most experts quoted in the media advised the same thing, partly because surfaces could retain the virus but mainly because kids are kids and are unlikely to maintain six-foot distances all the time. So yes, this became common advice, but it had nothing to do with the CDC.

This is all tentative since my trip back in time might have missed some important statements. And it's certainly true that, in general, the CDC tends to be very conservative in its advice and is slow to change it in the face of new evidence. You may decide for yourself whether that's good or bad.

That said, my tentative conclusion is that the CDC did a perfectly decent job on the subject of surface infections. The problem is that there were lots of other voices too, and it wasn't always clear to everyone what advice was coming from who. That's led to unfair recollections like this one in the New York Times last week:

When the coronavirus began to spread in the United States last spring, many experts warned of the danger posed by surfaces. Researchers reported that the virus could survive for days on plastic or stainless steel, and the Centers for Disease Control and Prevention advised that if someone touched one of these contaminated surfaces — and then touched their eyes, nose or mouth — they could become infected.

Americans responded in kind, wiping down groceries, quarantining mail and clearing drugstore shelves of Clorox wipes.

That's just not right. The CDC, I think, was pretty clear that you could become contaminated from these surfaces (which was true) but that it was pretty unlikely. When Americans went crazy for disinfecting their houses, it was because of advice from other media talking heads, not the CDC.

Other views are welcome. Let me know if you have media reports from last year that show the CDC providing different advice about the risk of getting COVID-19 from surface infections.

40 thoughts on “Homework Report: What Did the CDC Recommend About Cleaning Surfaces Last Year?

  1. DTI

    When the coronavirus that causes COVID-19 was first identified a lot of people (myself included) were concerned that it spread the coronavirus that causes the common cold spreads: by contact. If colds spread by face to hand and then hand to face and by large-droplets from sneezing, with surfaces as an intermediary step, then it made sense to sanitize the whiz out of everything.

    Meanwhile masks initially weren't thought to be much good except to remind you not to touch your face and maybe to contain sneezes.

    That wasn't *bad* advice. It was just incorrect. As more information came out it identifying it as airborne it became more clear that the masks that... we couldn't get... were a much better safety device.

    Sanitizing may have *become* kabuki but I don't think it started out that way.

  2. cld

    If sunlight kills the virus inside two minutes shouldn't it be recommended to hold classes and meetings out of doors or in brightly lit rooms whenever possible?

      1. Vog46

        And no one lights their rooms with UVC which is the light spectrum that kills the virus
        https://www.light-sources.com/blog/killing-bacteria-with-uv-light/

        Smaller versions of hospital use type UVC sanitizer light systems can fit into HVAC systems.
        The whole indoor outdoor discussion was NOT based on light but on air circulation. Indoors especially in classrooms you have a "captured" virus aerosols that are recirculated by the HVAC system. Outdoors the virus gets diluted by the general breezes. Indoors air circulates in a pattern where air is drawn in a specific direction, gets heated or cooled and recirculated in a specific direction. The same holds true for Churches, and businesses but on a much bigger scale.
        MOST UVC light is absorbed by the atmosphere before it reaches us - which is why the have to artificially create it using machines to disinfect hospital rooms effectively

    1. jeff-fisher

      the wikipedia article for 'lux' (the unit of light per area) has a good table.

      Direct sunlight is 100-300 times more intense than office light, simple daylight is 30-100 times. And that is not accounting for the fact that our lights are intentionally designed to avoid the more destructive wavelengths.

      That is why when you walk inside from a sunny day you often can't see at all for a few seconds while the eyes adjust.

  3. Special Newb

    Except by the time the analysis of the choir super spreader came out we knew damn well it was airborne. And CDC and plenty of other medicos refused to entertain the notion despite PLEADING FROM SCIENTISTS WHO STUDY AIRBORNE TRANSMISSION. Instead they made wild excuses for why that event was fomites.

    The CDC and WHO took months and months to officially change guidance to airborne. In fact this who situation maybe cause us to reevaluate whether colds really do spread by touch and not aerosols.

    1. Kevin Drum

      That's not really fair. The scientific community continued to be unsure of airborne transmission well after the choir event. And it wasn't just the CDC that continued to think that droplets were the main vector. Pretty much every country's CDC said the same thing.

      They turned out to be wrong, but when the scientific consensus finally coalesced, they changed their guidance. What more do you want?

      1. Vog46

        " but when the scientific consensus finally coalesced, they changed their guidance. What more do you want?"

        Why is it that majority rules (consensus) make this right?
        It's a NOVEL virus requiring thinking outside the normal cold/flu box. Health officials poo-poo'd the aerosol idea for months. That wasn't being wrong - that was IGNORING OTHER SCIENCE.

        Was the overall consensus about the earth being round in favor of that theory? NO. What about the earth rotating around the sun instead of the other way around? Granted they did not have the technological prowess we possess now but our medical/epidemiological community was too steeped in status quo virus knowledge that they THOUGHT they knew what caused COVID to spread w/o giving credence to those few who turned out to be right over time

        1. ScentOfViolets

          Blink. Uh, okay, I'll bite: just what, precisely, do you propose to replace the 'majority consensus of expert opinion'? No really, I want to know.

          1. Vog46

            They did not fund aerosol research nor did they pursue it with the same vigor they did for cleaning surfaces. This is old school cold and flu epidemiology talking
            They ASSUMED (falsely) that they were right
            It wasn't until the minority became very vocal that they did the research. Once they did the research they came to a consensus that the vocal minority was right all along
            Science should work on FACT not assumptions and that is exactly what they did - worked off a previous assumption that this virus was the same as the cold flu virus
            It was a novel corona virus - until it wasn't then it switched again

        2. wvmcl2

          It took centuries for any kind of consensus on the shape and movement of the Earth and solar system to emerge. We are talking about the events of a few months here.

          When a new and scary threat to public health emerges, I would give the authorities the benefit of the doubt when they perhaps exercise what we now see as an excess of caution. It's like the people who declare school snow days - they will be pilloried for being too lax or too cautious depending on whether the big snow comes or not.

          1. ScentOfViolets

            Sigh. You mean to say it's _not_ the accepted wisdom that the virus is spread primarily through airborne transmission?

            Not a big fan of the STEM disciplines I see. Also: Your source ... is not credible. Nor will it be until I can actually read it.

          2. ScentOfViolets

            No wonder you seem thick; you don't read so well. I didn't say I wouldn't read it, I said I couldn't.

            And don't think I didn't notice you not-answering my question, which I will repeat: You mean to say it's _not_ the accepted wisdom that the virus is spread primarily through airborne transmission? Yeah, you're 'special' all right. So special you get your own bus.

          3. Special Newb

            I assumed you wouldn't because I am not subbed to her or follow her and read it with no issue. So if there is some technical or geographical problem then perhaps you can access the lancet report which is now out.

            It's an indepth article refuting Drum's analysis.

  4. rick_jones

    Look, but don't touch.
    Touch, but don't taste.
    Taste, but don't swallow.

    As the science evolves it becomes difficult to track the changes and see them as something other than flip-flopping.

    1. ScentOfViolets

      So, they're flip-flopping _and_ they're zeroing in on the truth? At the same time? Something does not compute. As one of my professors once told the class, outside of mathematics, nobody gets it right. They just get less wrong.

  5. rick_jones

    When Americans went crazy for disinfecting their houses, it was because of advice from other media talking heads, not the CDC.

    From April 17, 2020:

    COVID-19 appears to spread person-to-person, through droplets that are expelled when a person coughs or sneezes and then are inhaled by a nearby person. Less often, it may be spread by touching an infected surface and then touching one’s mouth, nose, or eyes. Transmission may also occur before a person becomes symptomatic. As the CDC cautions, “COVID-19 is a new disease and we are still learning how it spreads.”

    Quoting from https://www.motherjones.com/kevin-drum/2020/04/heres-why-covid-19-is-worse-than-sars/ taking it from: https://www.biospace.com/article/comparison-2003-sars-pandemic-vs-2020-covid-19-pandemic/

    Less often, but nothing about how much less often - half as often, one-tenth as often? One one-hundredth? Absent of such clarification, and perhaps even with it, what will be heard is it can be spread through droplets person to person, and via surfaces. Because if you don't have a concrete statement, one has to assume the worst.

    1. rick_jones

      The full paragraph from the biospace article as it reads presently at least:

      COVID-19 appears to spread person-to-person via droplets that are expelled when a person coughs or sneezes and then is inhaled by a nearby person. Less often, it may be spread by touching an infected surface and then touching one’s mouth, nose, or eyes. Transmission may also occur before a person becomes symptomatic. Nearly six months after an emergency was declared, this transmission information has not changed.

      That article shows Published: Sep 07, 2020, and in the vein of my perennial advice to archive.org early, archive.org often, the wording in the original version:

      COVID-19 appears to spread person-to-person, through droplets that are expelled when a person coughs or sneezes and then are inhaled by a nearby person. Less often, it may be spread by touching an infected surface and then touching one’s mouth, nose, or eyes. Transmission may also occur before a person becomes symptomatic. As the CDC cautions, “COVID-19 is a new disease and we are still learning how it spreads.”

      just as it appears in Kevin's quote of the quote.
      In October, 2020 Mother Jones included: https://www.motherjones.com/food/2020/10/hygiene-theater-at-restaurants-is-creating-endless-plastic-waste/

      The CDC gave that claim a big boost in May, when it published its guidance recommending that restaurants use disposables.

      pointing at a page which presently says it is not being updated (and without the text itself) but for which there is an archive.org entry at: https://web.archive.org/web/20200510160418/https://www.cdc.gov/coronavirus/2019-ncov/downloads/php/CDC-Activities-Initiatives-for-COVID-19-Response.pdf There are many links therein to infection control write-ups. I've not tried to follow them but I assume at this point they would be best followed through archive.org.

      There is also https://www.motherjones.com/coronavirus-updates/2020/06/nearly-1-in-6-coronavirus-cases-in-illinois-could-be-tied-to-cook-county-jail/ which includes a reference to a suit claiming insufficient washing of surfaces.

  6. Citizen Lehew

    From the beginning until the present day I've found all advice regarding surfaces, CDC or otherwise, maddeningly contradictory, leaving me still in full on Howard Hughes mode.

    Even the most recent guidance follows the same pattern: "The risk of contacting Covid from surfaces is almost non-existent... BUT it's still a good idea to wash my hands regularly, and to clean high tough surfaces with soap and water."

    WHY?! Why would that be suggested at all if there's basically no risk? Is there an elevated risk from Covid on surfaces or isn't there?

      1. Citizen Lehew

        Yea, great... when you're trying to get clear guidance about avoiding a new pathogen it's not exactly the best time for general hygiene tips that may or may not apply to the actual deadly virus.

        1. Crissa

          No, because those general hygiene tips still work on a new pathogen.

          They don't just stop working because it's a new pathogen.

        2. ScentOfViolets

          Pipe down, Mr. Dobbs. You don't have a leg to stand on at this point. Nor will you until you produce actual, linkable evidence that the CDC was incompetent or willfully wrong.

          1. Citizen Lehew

            You should take your own advice on calming down. 😛

            I never suggested the CDC was incompetent or willfully wrong. They (and everyone) just had a tendency to always nullify their "surfaces are very low risk" messaging with a quick "but be sure to wash your hands and everything else anyway!" at the end.

          2. ScentOfViolets

            Chuckle. A couple a points here; a) telling you to pipe down in no way indicates any sort visible irritation, and b) it's an obvious play on words, given the J. R. 'Bob' Dobbs icob you see fit to appropriate.

            The fact that you didn't get it -- more precisely, that it went clean over your head -- does not indicate some intellectually nimble enough to be worth talking to.

  7. D_Ohrk_E1

    Current CDC guidance:

    "Consider the type of surface and how often the surface is touched. Generally, the more people who touch a surface, the higher the risk. Prioritize cleaning high-touch surfaces."

    Earliest CDC guidance (4/13/2020):
    "Clean surfaces using soap and water. Practice routine cleaning of frequently touched surfaces.
    High touch surfaces include:
    Tables, doorknobs, light switches, countertops, handles, desks, phones, keyboards, toilets, faucets, sinks, etc.
    ...
    If more than 7 days since the person who is sick visited or used the facility, additional cleaning and disinfection is not necessary."

    Has it changed that much?

  8. jjramsey

    Be careful with the study that said, "The scientists found that severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was detectable in aerosols for up to three hours, up to four hours on copper, up to 24 hours on cardboard and up to two to three days on plastic and stainless steel."

    That study started out by applying crazy high concentrations of SARS-CoV-2 onto surfaces (or the air) and then seeing how long it took to decay. That's not an irrational approach if one is trying to measure the half-life of the virus, since too low a starting dose may make it hard to measure the amount of virus remaining after a period of time. However, the study is probably not helpful for estimating the actual time that the virus will remain on a surface.

    See here for more details: https://ncse.ngo/can-i-catch-covid-19

  9. royko

    There were a number of factors that led to over-emphasis on surface sanitization.

    1) The study showing how long the virus could last on certain surfaces under the right conditions did freak everyone out a bit, even if "certain surfaces" and "under the right conditions" were doing most of the work.

    2) It was something that people -- and particularly businesses -- could easily do. This made people feel more in control and allowed businesses to say "Look at all we're doing to keep you safe!" It didn't really matter. It let them feel like they had more control.

    3) It was also something where most of the work got shoved onto people that usually do the dirty work: janitorial and maintenance staff, low paid retail workers, restaurant bussers and servers. A small segment of the population just had more work dumped onto their jobs, and everybody else could do as much or as little as they felt like. It was the most convenient counter-measure.

    4) And, of course, as the push to reopen businesses ramped up, it allowed a nice kabuki to let businesses argue that since they were "making things safe" they could reopen, and gave people a rationalization for going along with it.

    5) Lastly, it couldn't hurt, right? That was always the answer when you point out it wasn't really effective. I mean, someone COULD catch it from a surface, so cleaning surfaces might help a little bit? Even if it doesn't really change the risk at all (and may make it worse, because it gives people a false sense of security), it's hard to argue against sanitization in a pandemic.

    So it all fit nicely together. Even today, organizations I'm involved in are overstressing surface cleaning for their events.

    I can't really fault the CDC for this one. They kind of had their hands full anyway, with the President and a loud, angry segment of the population arguing we should reopen by Easter (around when our first wave was peaking!)

    1. ScentOfViolets

      _Real_ lastly: it turns out that the number of people getting seasonal respiratory infections dropped drastically. This last year is the only time in memory that I've had neither colds nor flu. Whoda thunk?

  10. jeff-fisher

    Key to that year old report of covid on surfaces is the word "detectable".

    It's hard for people who have never worked in a molecular biology lab to wrap their heads around how sensitive the methods can be. Pcr can make billions of copies from a handful of dna fragments of the correct sequence in a couple hours, and the usual procedure is to run the reaction until you expect it to run out of raw materials.

    It's all those brain teasers about exponential growth made real, even more ideally than the math of a pandemic.

    But, yes, the CDC always wishes we would wash our hands more.

    And there was value in not getting regular colds and the flu in the context of a respiratory pandemic. Reducing the noise.

    And simple measures like setting your non perishable groceries aside for a few hours or overnight after you get home and wash your hands takes a small risk down to nothing.

    What is stupid is when it gets cargo-cult like. "My employees have to come into work and if we get a reported infection we will "deep clean" overnight and then can keep making everyone go to the office!". That's pretending surfaces are the only problem and very likely all it's doing is increasing exposure for the people doing the cleaning and the people being put together on the excuse of the cleaning.

  11. gesvol

    FWIW, in reference to playgrounds, here is the guidance from the CDC website (the page was last updated in July):

    https://www.cdc.gov/coronavirus/2019-ncov/daily-life-coping/visitors.html

    "At playgrounds
    Close up of empty colorful swings at a playground
    Playgrounds are often crowded and could make social distancing difficult

    Follow the general principles listed above, plus the following….

    Carefully consider use of playgrounds, and help children follow guidelines.

    In communities where there is ongoing spread of COVID-19, playgrounds can be hard to keep safe because:

    They are often crowded and could make social distancing difficult;
    It can be difficult to keep surfaces clean and disinfected;
    SARS-CoV-2, the virus that causes COVID-19, can spread when young children touch contaminated objects, and then touch their eyes, nose, or mouth.
    If you choose to visit a playground:

    Maintain a distance of at least 6 feet away from people you don’t live with.
    Wash hands with soap and water for at least 20 seconds.
    Adults and older children who can safely use hand sanitizer: Use hand sanitizer that contains at least 60% alcohol and rub hands together until dry, if soap and water are not readily available."

    So they didn't say one or the other in regards to closing playgrounds. But they certainly are still referencing the difficulty of keeping surfaces clean and the risk of getting infection from contaminated surfaces. Once again, for whatever it's worth.

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