For much of my career in Infectious Diseases I was head of infection control for two hospital systems and one long-term care facility, a total of 6 institutions with differing levels of care and acuity. So I tend to see everything through the lens of infection and infection control.  Makes me fun at parties.

The goal of infection control is to, well, control infection. Kind of a duh. But it can be divided into preventing hospital acquired infections (surgical wound infection, ventilator acquired pneumonia, central line infections, etc.) and preventing the spread of contagion to staff and patients (influenza, COVID 45, chickenpox, etc.).

When I started in the biz, I thought the occasional hospital acquired infection was the price paid for high-tech invasive medicine. You can’t do what we do to people and not get the occasional infection.


My first hint was hand hygiene. It has been known for 200 years that hands are an excellent source to spread infections around the hospital and that handwashing stops the spread of germs. Despite that ancient knowledge, handwashing compliance with adherence -or is it adherence with compliance?- was abysmal.

There was one surgeon who refused to wash his hands or wear gloves for dressing change, and a medical specialist said it was too much of a bother as the sink was on the other side of the room. And the anesthesiologists? Jesus. Getting them to wash hands much less do full barriers for central line infections or alcohol wiping a medicine bottle was impossible, much less washing hands.

One of the good things about hospitals assuming physician practices is it standardizes good behavior, or you are gone. This was decades ago, and all of the above doctors are long gone. But it taught me early that a remarkable number of doctors are recalcitrant morons who willingly ignore best practice and the medical literature. As you read this, remember, that sometimes highly educated and trained doctors are unable to do the right thing.

Then came alcohol foam. At first, I thought it was like Easy Cheese , a convenient way to deliver alcohol and it was to be used orally. To my disappointment, I quickly discovered that it was better used on the hands. With only 20% adherence with compliance, infection rates fell by half. That was amazing. As compliance with adherence to using alcohol foam increased over time to 100%, the hospital infection rates fell in lock step.

The dose-response curve was interesting and unexpected, at least by me. And we really did get to 100%. The rule was you had to foam when entering and exiting a room. Period. And if noticed in real time, you would be (nicely) asked to foam, and the only response was ‘thank you.’ No whining, complaining, bitching or yelling allowed. I literally went to every nurse and doctor in the system to tell them the expectations and that if anyone complained about being asked to foam, they would be referred to me. I never got a referral.

Hand hygiene, combined with various targeted interventions for ventilator-associated pneumonia, line-related infections, catheter-related urinary tract infections, etc., drove our infection rates down to almost zero. In the early days of my practice, I made a living taking care of hospital-acquired infections; at the end? Almost nothing. It was nice to put myself out of work.

Around a decade ago, I realized that infections were not the price of doing business and that infection rates should be close to zero. Close, but not quite.

The problem was threefold. To keep infections at zero you have to do multiple interventions all the time, no fails ever aka perfection. Not humanly possible. Another is there would occasionally be some perfect storm of rare events that would combine to circumvent all our hard work. Microorganisms are wily creatures and will take advantage of even the slightest opportunity to start an infection.

And we do not always have control over patients’ behaviors after discharge and, to paraphrase Art Linkletter (anyone know what I am referring to here?), patients do the darnedest things and get infected.

The medical literature is filled with case reports and outbreaks of infections caused by the damnedest events and was one of the aspects of care that makes ID entertaining.

Preventing infections isn’t easy or simple. Multiple interventions, always done perfectly. But I am proud to say my hospitals were as close to perfection as is possible.

And it also depends on whether the organism can be part of the human condition or is only a pathogen. For example, besides hand hygiene, I am skeptical that outside of an outbreak, much of what we do to prevent the spread of MRSA or ESBL E. coli or other organisms that can be a normal part of our microbiome, does much to prevent spread. But for organisms that are only pathogenic? Much more important.

Which gets us to COVID 45, part of your complete infection control program and prevention in the real world.

All the cleaning and disinfection we do are mostly medical theater. COVID 45 is spread predominantly by aerosols/droplets. I do not doubt some poor slob has stuck his finger on some COVID laden snot and then placed that finger in his eye. Shit happens. You want to be grossed/entertained? Just watch people’s hands in a public space, say an OR break room. Fingers wander. But most successful interventions to prevent COVID spread are directed are the primary mode of transmission: the air.

So do masks work, and by work I mean prevent infection. Sure as hell do in the hospital. Well, mostly. I was initially surprised when I saw there were studies evaluating the efficacy of masks worn in the OR did not prevent infection.

From the limited results, it is unclear whether the wearing of surgical face masks by members of the surgical team has any impact on surgical wound infection rates for patients undergoing clean surgery.

But I considered. The organisms that cause surgical wound infections, Streptococci and Staphylococci, are not usually found in the upper respiratory tract. They can be. But not usually. It is rare for oral Streptococci to lead to infections from procedures. But Streptococci can jump from the HCW to patients, which is why masks are a good idea. Because, as noted, shit can happen. So I would prefer to have anyone doing a procedure to wear mask. Hopefully a new mask with each procedure. As a fellow I had a panic call from the OR. The surgeon had her mask around the neck during lunch and in the middle of an open heart a broccoli floweret fell from the mask and into the mediastinum. Largest cardiac vegetation of my career. The patient did fine; there should be nothing on a piece of cooked broccoli that can cause an infection.

But hospitals are controlled, aseptic environments where you have people like me pointing out your infection control failings in real time. The infected patient is in a fixed position, in bed most of the time, in a room with little for a pathogen to prosper and rapid air turnover. A hospital room has 6-12 air changes an hour, depending on the room. Air is pumped out of the rooms into the outdoors and with it pathogens, never reused. Makes the heating bill a bitch.

With knowledge of the predominant method of transmission (contact, fecal oral, droplet, aerosol, etc.), it is simple enough to throw together the necessary personal protective equipment to protect yourself from whatever pathogen the patient has. Each intervention does not lead to a binary result, it just decreases the odds of infection.

For what it is worth (little), 36 years of taking care of acute infections and I never caught one from a patient. I was up to by eyebrows in COVID and I have avoided that pathogen. So far. I did convert my PPD as a fellow, but I suspect it was a non-occupational TB exposure, from an unknown tubercular. Some data suggests that many healthcare workers PPD conversions are not work related. As one example

In the setting of an effective tuberculosis infection-control program, TST conversion rates were low, and the risk of conversion among HCWs was associated most strongly with nonoccupational factors.

Los Angeles and the county hospitals I frequented may not be the as TB free as one would like.

I can remember two respiratory outbreaks in my long and storied career. One was influenza, likely from a nurse who became symptomatic in the middle of their shift and spread flu to a few patients. And there was a chickenpox outbreak in one of our ICUs, the source never identified.

But otherwise no infections or outbreaks I can recall. I do not doubt there was the occasional transmission of flu or adenovirus or COVID or RSV from patient to staff, but it would be hard to know if these were acquired as part of work or part of life.

To my mind (lots of opinion to follow), trying to apply the concepts of hospital infection control to COVID was bound to be suboptimal or even ludicrous. I still think the 6-foot rule was stupid. It is fine for a hospital room, but in the real world people are constantly moving in and out of each other’s haze and air currents will take droplets and aerosols far from their origin.

Masks? I wrote the first draft in the Fiji airport waiting for a flight home from New Zealand, and the few who are wearing masks are wearing them poorly or the wrong ones.

It is, I think, clear, that masks, as well as other social distancing (like avoiding people inside as much as possible), stops respiratory infection transmission. Most respiratory viruses disappeared during COVID. China, following the lead of Florida, has seen the results of changing from maximal to minimal COVID prevention.

The recent Cochrane meta-analysis is, to my mind, worthless. I am not a big fan of meta-analysis as a means of coming to a truth of a matter. To my mind, the theory behind a meta-analysis is you collect multiple piles of cow manure into one large pile, and you get spun gold. Mmm. No.

A meta-analysis can offer a nice overview of a topic, but I have never found an expert in a field who thought a meta-analysis in their field of expertise was the last word on a topic. The more expertise in a field, the more you read the primary literature and try to apply it to patients, the less enthusiastic you are about meta’s. I use them like the proverbial drunk and a lamppost.

Masks to prevent respiratory infections in the community? There are a lot of questions around mask use as there are with vaccinations. Like all of medicine, it is complex.

“If you wear a mask while there’s a pandemic, are you less likely to get sick?”
“If you wear a mask while you have a respiratory illness, are you less likely to infect other people?”
“If you make people less likely to get sick during a pandemic, does that have lasting benefits to them, or does it just delay an infection without significantly changing their long-term health outcomes? Does it reduce transmission enough to change the overall dynamics of the pandemic?”
“If you tell people to wear masks, will they actually wear masks correctly and reliably?”


“If you mandate that people wear masks, will they actually wear masks correctly and reliably?”
“What are the costs, to the median person and to a person who is unusually affected by wearing masks, of wearing masks?”

My take, no surprise, is the better the mask and the more you wear it, the less the odds of getting a respiratory illness, including COVID 45. Add other protective interventions, the odds go down further. There are other opinions:

“There is just no evidence that they” — masks — “make any difference. Full stop.” Tucker Carlson.

Whoops. Wrong attribution, same credibility for me. It was Tom Jefferson, who said in the same interview.

The idea that the COVID virus is transmitted via aerosols has been repeated over and over as if it’s “truth” but the evidence is as thin as air.

Which begs the question: why does the Cochrane hire these authors? If you judge a person by the company they keep, it cannot be good for their reputation. Of course, it could be they like the opinions of a maverick. I saw Maverick recently. Awful. Predictable, cliché ridden, full of unbelievable plot holes, brain-dead. It looked good until you actually thought about it. Made Plan 9 From Outer Space look good in comparison.

Is that what the meta analysis showed? I plowed through the whole thing. Nope.

As noted above, it was extremely difficult to get highly educated and trained medical professionals to use protection correctly. Insert pregnancy joke of your own choosing here.

The key paragraphs in the article?

Adherence with interventions, especially educational programmes, was a problem for many studies despite the importance of many such low-cost interventions. Adherence with mask wearing varied; it was generally around 60% to 80%, but was reported to be as low as 40% (see Table 1). Overall, the logistics of carrying out trials that involve sustained behaviour change are demanding, particularly in challenging settings such as immigrant neighbourhoods or students’ halls of residence.

The identified trials provided sparse and unsystematic data on adverse effects of the intervention, and few of the RCTs measured or reported adherence with the intervention, which is especially important for the use of medical/surgical masks or N95 respirators. No studies investigated how the level of adherence may have influenced the effect size.


The observed lack of effect of mask wearing in interrupting the spread of influenza-like illness (ILI) or influenza/COVID-19 in our review has many potential reasons, including: poor study design; insufficiently powered studies arising from low viral circulation in some studies; lower adherence with mask wearing, especially amongst children; quality of the masks used; self-contamination of the mask by hands; lack of protection from eye exposure from respiratory droplets (allowing a route of entry of respiratory viruses into the nose via the lacrimal duct); saturation of masks with saliva from extended use (promoting virus survival in proteinaceous material); and possible risk compensation behaviour leading to an exaggerated sense of security

Given the adherence to mask use and other issues, this study is no different than comparing homeopathy to water.

You could reasonably conclude that mask mandates have issues or that infection control techniques used outside the hospital have adherence issues, rendering judgment on their efficacy problematic. That would be a reasonable response. A messy literature should lead to a messy conclusion. To conclude that masks don’t work? I wonder how it feels to have the blood on innocents on your hands?

But then, not even the Cochrane agrees with the Cochrane:

one of the lead authors of the review even more seriously misinterpreted its finding on masks by saying in an interview that it proved “there is just no evidence that they make any difference.” In fact, Soares-Weiser said, “that statement is not an accurate representation of what the review found.”

I remember as an intern discussing whether a study that looked at upper GI endoscopy was helpful for upper GI bleeds. The study said no, but my GI attending pointed out no intervention to stop the bleeding was done. They just looked, said yep, there’s bleeding, and removed the scope. There has to be an intervention before you can declare it is of use or not. And a chin mask doesn’t cut it.

If you have highly infectious diseases, as most respiratory viri are, and you are not OCD punctilious with your infection control, no prevention is going to work. It was really difficult to get proper prevention methods in HCWs. In the real world? Forgetaboutit.

I was going to use seatbelts as my go to example, figuring that everyone uses seatbelts, 100% adherence, and how combined with multiple other engineered safety features cars have become remarkably safe compared to the 1950s. A nice metaphor for infection prevention, I assumed there would be nice before and after data as everyone would use seatbelts to avoid the annoying chime.


People don’t wear their damn seatbelts.


And use of seatbelt reminder systems only increases seatbelt use a few percentage points.

The Cochrane reviews have never done a meta-analysis on seatbelt use. I assume if they did, they would use the same methodology and ignore whether seatbelts were actually used correctly, just if seatbelts were in the car. And I assume they would conclude

“There is just no evidence that they” — seatbelts — “make any difference. Full stop.”

It’s all about the odds. Depending on the infection, various interventions, if done correctly, will decrease the odds of spreading infection. The more interventions you apply and the more adherent with compliance you are, the better the results. And it is a royal pain in the neck to do correctly and consistently. In the real world, compared to the hospital, interventions will likely be less than impressive because adherence with compliance will stink on ice. Infection control will be done haphazardly, at best.

Still, I wore an N95 on the plane and in the waiting areas. I avoid people if I can. The best thing about COVID was I had a great excuse to avoid people, which I prefer to do anyway. And I don’t inhale. Learned that from Clinton.

COVID 45 was and is horrific. It has killed 7 million people and is still killing around 1000 people a day. Around a 0.1% death rate. But that’s nothing. Influenza killed maybe 5% of the world in 1918-1919. In three months. In a slow moving, relatively empty, world. Flu will return, and avian influenza is waiting its turn to become infectious as well as fatal.

When, not if, we get a respiratory infection that is both highly contagious and has a 5, 20, 50% mortality rate, we will need every intervention to slow the infection down, please. And people will look at nonsense like erroneous takes on the Cochrane reviews and those interventions will not be used. And a lot people will die unnecessarily.

Full stop.


  • Mark Crislip, MD has been a practicing Infectious Disease specialist in Portland, Oregon, from 1990 to 2023. He has been voted a US News and World Report best US doctor, best ID doctor in Portland Magazine multiple times, has multiple teaching awards and, most importantly,  the ‘Attending Most Likely To Tell It Like It Is’ by the medical residents at his hospital. His multi-media empire can be found at

Posted by Mark Crislip

Mark Crislip, MD has been a practicing Infectious Disease specialist in Portland, Oregon, from 1990 to 2023. He has been voted a US News and World Report best US doctor, best ID doctor in Portland Magazine multiple times, has multiple teaching awards and, most importantly,  the ‘Attending Most Likely To Tell It Like It Is’ by the medical residents at his hospital. His multi-media empire can be found at