Controversies in Hospital Infection Prevention

Friday, July 17, 2020

COVID-19 Transmission: Medicine Grand Rounds at UCSF

Tuesday, July 7, 2020

Let's Just Get Every Face Covered

Photo by cottonbro at pexels.com

In the over decade-long history of this blog, Dan's recent post, A Tiresome SPAT, has been viewed more times than any other post we've ever written. And it's only been up 48 hours. This is a testament to Dan's ability to encapsulate the controversy regarding SARS-CoV-2 transmission in a billiant way. As I reflected on his writing, it became increasingly clear to me that the source of the controversy of whether we are dealing with droplet transmission or aerosol transmission is deeply rooted in the framework through which you're viewing the issue. These frames are associated with different values and ways of thinking, and depending on the frame utilized determines your recommmendations for mitigating transmission.

The first framework I'll describe is the medical (i.e., individual patient) frame. Imagine a patient visiting their physician and asking what they can do to best avoid COVID-19 infection. In addition to social distancing and hand hygiene, the physician would likely recommend a mask and eye protection. The physician might even recommend an N95 respirator depending on the patient's underlying conditions, the context of their exposures, and the patient's risk tolerance. In general, in this framework, risk tolerance is low, and the goal is typically to reduce the individual's risk to the irreducible minimum. This approach drives the occupational health perspective. PPE is viewed from the standpoint of efficacy--how do we provide ideal protection?

Now, let's look at the public health (i.e., population) framework. From this perspective, the goal is not necessarily to prevent every possible case of COVID-19, but rather to bring the outbreak to an end. This requires reducing the R0 to less than one. Thus, the interventions don't need to be perfect, and individual risk is tolerated to a somewhat greater degree. And in this framework, the PPE recommended is that which is most effective (i.e., how well does it work in the real world?), which factors in adherence. Let's say that face covering A is 90% efficacious, but only 20% of people are willing to wear it. On the other hand, face covering B is 60% efficacious, but 80% of people are willing to wear it. We're clearly better off with face covering B. The public health framework is driven by a utilitarian perspective--accomplishing the greatest good for the population, not for any given individual patient.

Our recent JAMA viewpoint, Moving Personal Protective Equipment into the Communnity, in which we argue for universal face shields in the community settting, was written from a public health framework. This was perhaps not clear to the many individuals who pointed out that in some cases there could be airborne transmission of the virus for which a face shield may not work. Yes, we get that, but the epidemiology convinces us that the airborne route is a minor mechanism of transmission.

The bottom line here is that we can't let perfect be the enemy of the good. We recommend influenza vaccine every year despite an average seasonal effectiveness of approximately 40%. The best face covering is the face covering that people will wear. Though I personally favor face shields for community use, I am happy to see faces covered in almost any way possible (which is why I love the photo above).

And if it's not bad enough that experts are not in agreeement, we have the additional problems of botched messaging by the CDC and political leaders who by intentionally sowing doubt and refusing to be good role models, make this work all the harder. Kudos to those leaders who are mandating face coverings. And my message to everyone is this: for community settings, let's just get everyone in a face covering now, whichever one works for them. After the pandemic is over, we can sort it out once and for all.

Sunday, July 5, 2020

A tiresome SPAT

I’m surprised that we can’t stop arguing about the modes of SARS-CoV-2 transmission, despite the fact that most experts (including our friends at WHO) agree on the important issues. Our colleague Jorge Salinas very nicely summarized these issues (and their implications) in this post.

The latest kerfuffle: media coverage of 239 experts who are upset that the WHO is not acting as decisively as they’d like on an evidence base that the experts themselves admit is far from definitive.

As we’ve outlined here and here, a major problem plaguing this discussion is the false dichotomy between “droplet” and “airborne” transmission that we use in healthcare settings (for simplicity of messaging, and because it has served us well for several decades—for reasons I’ll get back to later). This dichotomy divides application of transmission-based precautions between those pathogens spread via respiratory droplets, all of which must absolutely fall to the ground within 6 feet of the source, and those pathogens which become airborne, meaning they travel long distances on air currents, remain in the air for very long periods of time, and most importantly, can cause infection after their airborne sojourns if they find the right mucosal surface.

But we know (and WHO experts know) that there is no such dichotomy—it’s more of a continuum. At the very least there is a middle category, let’s call it Small Particle Aerosol Transmission (or SPAT). Many respiratory viruses (not just SARS-CoV-2) can remain suspended in aerosols and travel distances > 6 feet. As Jorge outlined, it’s probable that transmission events occur when these aerosols are concentrated in closed, poorly ventilated spaces or in very large amounts (e.g. a 2+ hour choir practice, a 3 hour indoor birthday party, a crowded bar). This may explain the superspreading events that drive a lot of SARS-CoV-2 transmission.

It’s important to distinguish SPAT from “classic airborne transmission” (let’s call it CAT). The CAT pathogens (TB, measles, VZV) have very different transmission dynamics than SPAT pathogens, as I outlined here (R0s of >10, household transmission rates of 50-90%). The distinction is important because for most healthcare epidemiologists, using the term “airborne” implies a common set of “one-size fits all” interventions to prevent transmission, interventions that require resource-intensive engineering controls and PPE requirements. It is not at all clear that such interventions are required to prevent transmission of SPAT pathogens. In fact, most evidence (and real world experience) suggests that they are not. This is why the droplet-airborne dichotomy has served us fairly well over the years—either because droplet precautions appear to be pretty effective at preventing SPAT, or because SPAT is rare even among those viruses capable of it.

I could say more about my feelings about aerosol-scientists criticizing epidemiologists and clinicians for having an “overly medicalized view” of the evidence, but I don’t want to be CAT-ty. I just want to end the SPAT.

So let’s redirect the discussion instead to: with the limited information we have, what additional interventions should WHO and/or CDC recommend for transmission prevention during the pandemic? Masks in crowded indoor spaces? Sure, but avoiding such spaces is preferred. Improved ventilation in all indoor environments? Absolutely, let’s get to work on that. N95s in the community? Don’t make me laugh, it might generate aerosols.* N95s for all patient care? Fair to consider, but by now we’ve gathered quite a lot of experience safely delivering care using existing WHO recommendations. And as Jorge aptly pointed out, “a debate only centered on whether respirators or medical masks are needed can distract us from the bigger challenges.” Indeed.

*Clarification as this comment, made in jest, has been misinterpreted. N95 masks do not generate aerosols. They are unrealistic for community use, as they must be fit-tested and worn properly (even if we had an unlimited supply, which we do not). Nor are they, in my opinion, necessary for community protection. Face shields or medical/cloth masks are preferred for community use.

Thursday, June 18, 2020

COVID-19 Can Have Airborne Transmission but You Don't Need to Run for an N95

This is a guest post by Jorge Salinas, MD, Hospital Epidemiologist at the University of Iowa Hospitals & Clinics.

There is virtually no doubt that SARS-CoV2 is transmitted by droplets and contact. However, the debate continues about whether SARS-CoV2 can be transmitted through the air, in what epidemiologists call “airborne transmission.” As with most biologic processes, unfortunately this is not a dichotomy. Many (too many) factors play a role.

Population density matters. As people breathe, speak, sneeze, or cough we all produce many particles that have a continuum of sizes. These particles are unfortunately called too many names in the literature and the lay press (e.g., droplets, aerosols). Viruses and biologic processes don’t read textbooks. These particles can be large (what healthcare epidemiologists call “droplets”), medium size (no fancy name for them), and small (these are called “aerosols” by some but “droplet nuclei” by others). If we are near only one infectious person, the number of small particles (aerosols) expelled may not be enough to meaningfully contribute to infection. But if we are exposed to many infectious people at once, the number of small particles can increase. In such instances, airborne transmission in addition to contact and droplet transmission can play a role in outbreaks.

Patient characteristics are also tremendously important. Some may extrapolate that COVID is not as contagious or rule out the possibility of airborne transmission because of a paucity of hospital outbreaks, even if not following airborne precautions. If we follow the natural history of COVID, we now know that a person is possibly infectious 48 hours before symptom onset. Most people do not require hospitalization, and those that require hospitalization may be in later stages of the disease. We are learning daily that COVID, the disease caused by SARS-CoV2, is likely a continuum. Initially, the disease is predominantly caused by direct injury of the virus to tissues, but as days go by some patients will have immunologic or para-infectious syndromes that may require hospitalization. By the time a patient with COVID requires hospitalization, their infectiousness has likely decreased. It is now clearly recognized that presence of viral RNA does not equal risk of transmission in many cases.

The setting is also very important. How big is the space where the infectious person and their potential contact are located. If outdoors, the risk is tremendously decreased as air flows freely greatly decreasing the possibility of breathing “the same air.” Indoors, the number of air exchanges is very important: the more air exchanges, the lesser the likelihood of spread. Fortunately, most hospitals have already implemented an increased number of air exchanges likely decreasing the possibility of airborne transmission of pathogens in hospitals.

If airborne transmission plays a role in SARS-CoV-2 transmission, I believe it is predominantly in the early stages of the disease, in the viral phase. That may explain why most healthcare outbreaks have occurred in nursing homes and long-term care facilities. Not only because of potential infection prevention deficits but because patients are already in the facility when they become infectious. They are at the peak of infectiousness when in the facility. Hospitals on the other hand, will usually admit patients days or even weeks after the beginning of the infectious period, likely attenuating the risk of transmission in hospitals.

Recognizing that SARS-coV2 can also spread via small particles should not lead to panic. It should lead us to modify our behaviors in the community by avoiding crowded indoor settings, using universal source control with face coverings, and maintaining physical distance.

Modified from CDC.

In healthcare facilities, we need to continue educating stakeholders about the hierarchy of infection controls. Administrative and engineering controls are by far the most important measures. Decreasing population density, protocols for early identification and isolation of potentially infectious cases, especially those early in the disease course, and increased air exchanges are likely the most important measures. Personal protective equipment is also important. However, a debate only centered on whether respirators or medical masks are needed can distract us from the bigger challenges of administrative and engineering controls.

Reducing population density in healthcare facilities (patient census and personnel) can lead to increased safety but has a tremendous impact on population health (less capacity to take care of patients) and potential economic implications if healthcare personnel numbers are decreased. Engineering controls are also costly but fortunately most hospital design standards already address increased air exchanges compared to regular buildings and homes.

This pandemic has been challenging for all. COVID-19 keeps me humble as what I thought I knew yesterday may not be true today. Let’s all remain humble and nimble as we respond to COVID-19 in the community and in healthcare facilities.

Saturday, June 6, 2020

Need a Face Shield?

Over the past few months, numerous people have contacted me to ask where they can purchase a face shield. I've assembled a list of some companies below. I'm sure there are many more, which I'm happy to add if you send me an email.

Standard Shields:

Industrial shields:

Shields that attach to baseball caps:

Hats with built-in shields:

Fun ones & kids' shields:

Shields designed to be worn with loupes:

Shields with goggles:

Eagle Eyes

DIY Face Shields:

Shield bulk orders:

Tuesday, April 14, 2020

Lessons from a Pandemic: Part 2

Photo by Volodymyr Hryshchenko on Unsplash

Three weeks ago, I wrote a piece on the lessons I learned from the beginning weeks of the COVID-19 pandemic in Iowa. You can see that here. If any of you feel like I do, three weeks in COVID time seems like a year. It has the feeling of a chapter from Einstein's Dreams. In ordinary time my week has a rhythm to it, with different meetings and activities on different days. Certain nights we go out for dinner. Now, every day is nearly the same at work and after work. It's all COVID, all the time. I sometimes wonder what normal life will be like but it seems so distant that I find it hard to imagine. I know that at some point this will end but it doesn't seem near enough to be real. It's like being in a surreal time warp that could have been an episode from the Twilight Zone. OK, enough weirdness. Here are my latest lessons:

Working at home truly increases efficiency. For the first time ever, I worked at home for an entire week. Previously, I had never worked at home for more than a day, and only if I had a project that required intense focus or a need to get it completed quickly. I had multiple Zoom meetings every day and gave four lectures by Zoom. What I now realize is that the many interruptions in my work day, with all the starting and stopping and the re-start after every interruption really reduce efficiency. At the hospital most of my meetings involve a 5-10 minute walk each way and when you have numerous meetings that adds up. And along the way you stop for unplanned chats that increase walking time. I also feel the need to check in with people that I work with and discuss current work issues. That's a good thing, but I now have a better view of how all of this impacts my workflow.
Medical care doesn't necessarily need to be face-to-face. Last week I had my first telemedicine clinic. I had done telemedicine inpatient infectious diseases consults for small community hospitals in the past but never outpatient clinic. It worked very smoothly. For most patients, particularly those with known problems, auscultation, palpation, and percussion don't add all that much. Once the outbreak is over, it will be interesting to see how many clinic visits return onsite. With advances in technology, patients can have BP cuffs that transmit readings, pulse oximieters, and even wireless stethoscopes at relatively low cost, making good assessment in the patient's home much more achievable.
Determining what is and is not an aerosol-generating procedure (AGP) needs to be thoroughly explored in future research. See these two excellent posts by Tom Talbot here and here to read more about AGPs.
In times of crisis, healthcare workers' risk tolerance is greatly reduced and risk perception is not always rational. This is natural given all of the information on the outbreak, much of it scary, that comes at us 24/7. There is a cry for zero risk, even though that is likely not achievable. In an effort to advocate for their constituencies, professional societies have added to the anxiety and created more demand for resources that are already scarce, such as testing supplies and personal protective equipment.
Once and for all, we need to determine the utility of every item of personal protective equipment for various types of pathogens. This will require federal funding to do the needed research. New designs should be evaluated and current PPE improved.
The focus of infection control and prevention research has been too focused on bacterial pathogens. Looking at journals from the last decade, one can see that most of the papers are focused on drug-resistant bacterial pathogens. These organisms pose little risk to healthcare workers. As above, federal funding will be needed to accomplish the needed work.
CDC has not been helpful by producing confusing information that is not practical, and SHEA and APIC have offered little to no guidance at a time when it is most needed. In contrast, the World Health Organization has produced guidance that is based on sound logic and written in a very clear manner.
Anthony Fauci is a hero. Where would we be without him? Don't think about the answer to that question.

More to come. Stay safe, everyone!

Mike

Saturday, April 11, 2020

The Face Shield Strategy: Moving to the Community

REUTERS/Athit Perawongmetha

With the assistance of a great supply management team, we have been able to outfit all of our clinical staff with face shields. See here for our rationale and implementation. Acceptance by healthcare workers has been good and compliance is easy to visually monitor. Our message is that the shields are to be worn at all times except when eating or when in a room alone. Shields alone are worn for non-COVID care. For the care of COVID patients, masks are added beneath the shield, except in the instance of aerosol-generating procedures, when N95 respirators are worn beneath the shield.

This week CDC recommended the use of cloth masks for all persons in public settings. Although cloth masks are better than nothing, depending on the material, the filtration efficiency varies, and they can become contaminated. Moreover, adjusting the mask increases the frequency of touching the face, which can lead to autoinoculation if the hands are contaminated. We're not very excited about this strategy. However, we believe that face shields offer a better solution for the public. Dan and I laid out the case for this in an OpEd in the Des Moines Register this week.

The advantages of face shields are their durability allowing them to be worn an indefinite number of times, the ability to easily clean them after use, their comfort, and they prevent the wearer from touching their face. Importantly, they cover all the portals of entry for this virus--the eyes, the nose, and the mouth. Moreover, the supply chain is significantly more diversified than that of face masks, so availability is much greater. Large companies, such as Apple, Nike and John Deere, have converted production lines to make face shields. Smaller companies, such as Upstaging, have as well. Upstaging is selling shields to consumers as well as hospitals. (I ordered some from them and received them in less than 24 hours.) Because the design of face shields is simple, massive production should not be difficult. Individuals and groups are making them via 3-D printing, and they can even be made from materials that are readily available from stores that sell office or craft supplies. Our goal should be to have a face shield for every person in the country. It should be worn anytime a person leaves their home, while in any public place, and even at work. From news reports, it appears that face shields are already being more commonly worn in other nations, particularly in some Asian countries.

Some argue that face shields may not prevent infectious aerosols that could be propelled around the edge of the shield. However, it appears that with this virus, transmission occurs mostly via droplets that do not have the ability to move in air currents and waft around the shield edges. But importantly, if everyone is shielded, these aerosols would need to move around the shield of the infected person and then waft around the shield of the uninfected person for infectious droplet nuceli to land on their face. The probability of this happening seems low, particularly since persons who are symptomatic and coughing should not be leaving their homes anyway. And hand hygiene still needs to be stressed to prevent autoinoculation.

Some are critical of any strategy that isn't perfect. But let's think about the influenza vaccine. Although the effectiveness varies from year to year, on average it's 40%. We push this vaccine hard in the hospital and in the community. Could we expect that face shields are at least 40% effective in reducing the transmission of COVID-19? I think so. Universal shielding would bend the curve more quickly and accelerate the ability to reduce social distancing and restrictions on movement.

Face shields are a simple solution that if implemented universally would have a major impact on public health. Until we have a vaccine, this may be our best intervention for preventing transmission in the community.

Addendum: See our viewpoint, Moving Personal Protective Equipment into the Community, on this topic in JAMA.