Our collective knowledge of COVID-19 has evolved rapidly since the pandemic began. Even as an Infectious Disease physician, I have often found it difficult to keep up with pertinent daily updates – especially in the earlier days when public heath recommendations could literally change overnight on the basis of a new study. We are now reaching a point where many of the key recommendations on measures like masking and social distancing have pretty well stabilized, so I think it’s a good time to catch up my colleagues in healthcare. It’s understandable if you’re feeling a bit behind. My entire career revolves around infectious issues, and I still occasionally find myself asking “wait, when did we change that?” Here are some of the more pertinent COVID-related issues that need updating among healthcare workers:
Test results are actually pretty reliable now
Just a few short months ago, our SARS-CoV-2 PCR tests were widely estimated to be only 60-70% sensitive. (For clarity, SARS-CoV-2 is the virus; COVID-19 is the disease it causes.) More recently, a large study of PCR testing for COVID-19 in the US suggested that current assays have a false negative rate under 5%, so test results can be viewed with a lot less suspicion. Even rapid tests like Abbott’s ID NOW are estimated to have a false negative rate around 15%. While this this isn’t great accuracy, it’s still a better detection rate than we once attributed to our “gold standard” PCR tests, only now with a much faster turnaround time.
Antibody tests preliminarily appear to produce reliable results as well, based on studies where people with known COVID-19 by PCR get follow up antibody testing. However, I do not routinely recommend antibody testing at this point because I have to ask – what does it change? We’re starting to see more convincing cases of people getting COVID twice due to mutations in the viral structure over time, so a positive antibody test doesn’t necessarily mean you’re immune. Yes, it’s a pretty good indicator that you had COVID-19 more than a couple of weeks ago, so I suppose you could pay several hundred dollars out of pocket to satisfy your personal curiosity (insurance companies aren’t paying for antibody tests thus far). I wouldn’t be surprised if, one day in the not-too-distant future, we start using a particular SARS-CoV-2 antibody titer to show who has had an adequate immune response to vaccination (similar to what we do with Hepatitis B now). Otherwise, I would say to save your money when it comes to COVID antibody testing.
You don’t need two negative PCR tests to declare someone non-infectious
This requirement made sense in the days when PCR testing was suspect, and we had no idea how long infected patients remained contagious. However, testing accuracy and our knowledge of SARS-CoV-2 transmission have evolved significantly in the months since the pandemic started. Research on viral transmission has found that the overwhelming majority of COVID-19 patients stop shedding viable virus by the tenth day of illness, even when they have persistently positive PCR tests. In fact, the CDC changed its isolation recommendations for most people to ten days from onset of illness, provided that symptoms like fever and shortness of breath are improving by that time. Some severely ill or immunocompromised patients may take longer than ten days to show improvement in COVID-19 symptoms, but basically, if a patient is getting better, and it’s been at least ten days since their symptoms started, they no longer need any special isolation precautions.
Widespread reliance on the “old” method of clearing someone from COVID-19 isolation has proven problematic for healthcare logistics. I’m sure we’ve all encountered it by now – the administrator of a nursing home or assisted living facility won’t allow a patient to return from the hospital until they have two negative nasopharyngeal PCRs in a row, even when the patient has recovered clinically and is well past the onset of illness. I have personally seen patients with positive PCRs out to six or eight weeks from initial diagnosis despite resolving their symptoms and otherwise doing well. This is an enormous waste of acute care and COVID testing resources – having patients occupy a hospital bed receiving serial test results that don’t really tell us anything. PCR positivity does not equal infectivity, and we should all be shifting to a time- and symptom-based isolation strategy at this point.
There is no blanket 14-day isolation/quarantine period anymore
First, a quick note: in public health terms, isolation is where you take measures to keep an infected person from spreading their disease to others; quarantine is where you separate seemingly healthy people from the general population after a disease exposure to see if they get infected. We tend to use these terms interchangeably (I know I’m guilty of it as well), but there you have it.
Shifting guidelines on this issue have generated a lot of confusion over time, so let me summarize the latest recommendations. As above, if your illness has gone on for at least ten days, and your symptoms are improving, you can stop isolating yourself. If you screened positive with no symptoms, isolate for ten days and call it good…unless you start developing symptoms shortly after the test – in that case, you restart the ten-day clock from onset of symptoms. If you have a condition that compromises your immune system, or if you had a particularly severe case of COVID-19, the key point is that you should isolate for at least ten days, since your symptoms could take longer to improve. In the uncommon event that symptoms drag on much longer than that, 20 days is considered the maximum isolation period. Helpful endpoints include no fever for at least 24 hours (in the absence of taking medication to reduce fever), reduced cough frequency and improved shortness of breath. If you can check those boxes, and it’s been at least ten days since your symptoms started, it’s time to venture outside the house again.
The 14-day recommendation still applies to those who have close, unprotected contact with someone known to have COVID-19. This is because 14 days is on the long end of observed incubation times for this virus. If you don’t test positive and/or develop symptoms by 14 days out from exposure, you’re most likely in the clear (at least for that particular event). Determining who needs to go into quarantine in this context can still be tricky because there’s some gray area regarding what constitutes an exposure. If you’re masking and keeping your distance consistently, this mitigates a lot of the risk from sharing a space with someone who is infected, particularly if that person is masking too. Of course, someone who knows they have COVID-19 really shouldn’t be out in public, even with precautions – this applies more to a situation where your contact is pre-symptomatic (they’re going to get symptoms of COVID-19, but they aren’t aware of them yet). We know people can shed SARS-CoV-2 for 48-72 hours before symptoms start, so if you find out a co-worker tests positive after your four-hour meeting in a stuffy conference room, that might qualify you for self-quarantine.
Consulting with a public health or infectious disease expert can be invaluable in making quarantine decisions like this. To give you an idea of the complexity involved, I couldn’t give a blanket answer for my own scenario above without a lot of additional information. How big was the conference room? Were the people in the meeting sitting more than 6 feet apart? Were there activities that might have brought them into closer contact? Was everyone masking? What type of masks were they using? Did everyone wear the masks correctly for the duration of the meeting or were people pulling them down to talk? Was the infected person sitting quietly in the corner or giving a presentation to the rest of the group? Is the exposed person a healthcare worker who could go on to infect even more vulnerable people? If it feels like you haven’t been able to get a straight answer on COVID quarantine protocols, this should give you an idea why.
You only need an N95 or PAPR in very select situations
This has been a topic of much debate over the last six months, and, while we do have studies showing that airborne transmission of SARS-CoV-2 is possible, our practical observations have not shown that it is very likely. I say that because studies making the case for airborne transmission are performed in controlled environments with experimentally-generated droplet nuclei that do not necessarily reflect what happens in the real world. During the Ebola virus epidemic, we had studies showing that it, too, was capable of remaining suspended in tiny droplets and potentially being transmitted by the airborne route. However, decades of observing Ebola transmission dynamics has shown us that this is simply not how the virus spreads in real life. Similarly, we already have multiple large studies showing that use of medical masks (not N95s or PAPRs) and social distancing significantly reduce transmission rates of COVID-19 in healthcare settings and in the population at large. If airborne transmission played a major role in spreading SARS-CoV-2, we would not expect to see such a profound effect of routine masking and social distancing, since airborne-sized droplets could pass through a standard surgical mask and remain suspended in the air for distances greater than 6 feet (2 meters).
Higher-efficiency masks like N95s are still utilized in healthcare situations that generate a lot of respiratory droplets, such as bronchoscopy or tracheostomy care. The CDC currently recommends using an N95 or PAPR whenever possible in the healthcare setting, although it acknowledges that medical masks are an acceptable alternative. The WHO recommends medical masks across the board. In general, a standard medical/surgical mask (worn correctly) offers good protection when it comes to preventing transmission of SARS-CoV-2. We have yet to see a head-to-head trial of N95 versus regular medical mask use during routine patient care, but I suspect it’s coming, since high-efficiency masks are significantly more expensive to acquire and maintain. My prediction is that N95s will be only marginally better, with the greatest difference seen during aerosol-generating procedures like those mentioned above. In the meantime, we must weigh the (likely small) benefit of high-efficiency masks against their significantly higher costs, higher labor requirements (fit testing, cleaning, maintaining a PAPR cart) and lower availability worldwide. In case you’re wondering, I personally use a standard surgical mask in routine patient care, and I feel comfortable with it (literally and figuratively).
You’re highly unlikely to get COVID-19 in an outdoor setting
Location can have a huge impact on risk for viral transmission – primarily indoors versus outdoors. For respiratory viruses in general, the odds of transmission go up in smaller spaces with fewer ambient air cycles. Outdoors, exhaled droplets of all sizes are quickly dispersed by the slightest breeze. While we don’t know the exact infectious dose for SARS-CoV-2 (the number of viral particles you need to inhale to get sick), this number is generally in the hundreds to thousands for other respiratory viruses. Even if you happen to inhale a handful of SARS-CoV-2 particles while talking to someone outside, it’s unlikely to lead to infection. Consider one large study published in the early days of COVID in China, before widespread masking and social distancing policies – out of 7,324 cases of COVID-19 traced back to their sources, only one was felt to be likely transmitted outdoors (0.0001% of cases). Unless you happen to be in a large, tightly-packed group of people (and you shouldn’t be these days), wearing a mask outside probably adds very little, if anything, when it comes to decreasing your personal risk for acquiring or transmitting SARS-CoV-2.
You’re unlikely to get COVID-19 from a contaminated surface
Contact with contaminated surfaces appears to play a comparatively tiny role in the transmission of COVID-19. Yes, there are studies reporting that SARS-CoV-2 can live on various surfaces for days at a time, but these studies use very large quantities of viral particles in tightly controlled environments. From our real-world observations, most infected people are unlikely to deposit that much virus at one time – especially if they’re masking, which they should be in public now. At the same time, environmental factors like UV light and heat frequently inactivate the virus in as little as one to two hours. While regular handwashing is always a good idea, we have grossly overblown the risk of acquiring COVID-19 from touching the environment. In healthcare and other industries, it’s generating a marked increase in waste from implementing more disposable containers and throwing away reusable objects like pens after a single use.
Let’s take a look at the sequence of events that would need to occur for someone to get sick from a contaminated pen. The infected user would need to cough or sneeze into their writing hand, or maybe use their writing hand to wipe away facial secretions, then forego washing their hands before handling that pen at the check-in desk. Healthcare businesses, in particular, should be requiring their patrons to wear masks and perform hand hygiene upon entry, making it much harder for these events to occur. Even if SARS-CoV-2 managed to make it onto the surface of the pen, it would likely be a very small quantity of virus compared to the amounts we see spread through the air. The unsuspecting victim of transmission would need to handle the pen relatively quickly, before environmental factors like UV light and heat start to inactivate the virus. They would then need to forego washing their hands as well and touch the contaminated area of the hand near their eyes or mouth with a large enough inoculum of viable virus to lead to infection. Once again, if everyone is masking and performing routine hand hygiene, this chain of events is very unlikely.
Oh, and "don't touch your face" really isn't practical advice - it's often reflexive, and you're going to do it no matter how hard you try. If you wear a mask and wash your hands, it won't matter.
I like pragmatic, evidence-based solutions when it comes to disease management. Each of us washing our hands, for example, is a lot easier, cheaper and probably more effective than converting everything in our environment to single-use or compulsively cleaning our surroundings. Each of the items on this list rightfully generated concerns in the earlier days of the pandemic because we lacked the experience to speak to them with confidence. As our understanding evolves, however, so should our practices. The non-medical public looks to healthcare workers for answers in these anxiety-provoking times, so let’s do our best to keep up with the science.