You don't need to catch that wave
There may be a lot of SARS-CoV-2 circulating during a wave, but you and your family are not at the mercy of inevitable infections
If you are reading this right now, there’s a good chance that your part of the world is experiencing yet another significant surge of COVID infections. Perhaps this is the sixth, seventh, eighth, ninth or even tenth wave where you are. The lack of efforts by governments and public health officials to mitigate the virus may make it feel like everyone is doomed to be infected one or more times per year in perpetuity. And again, if you are reading this, you surely know that is not something you want for your own health, that of your loved ones, or those of people in your community. We are still learning about the long-term impacts of (repeated) COVID-19 infections, but already the picture is not pretty. Contrary to much public health messaging, COVID-19 infection is not simply “like a common cold” or “no worse than flu” — but neither is infection inevitable, even during a wave.
The first thing is to let go of “all or nothing” thinking. Here’s why:
It matters how many times you get infected. SARS-CoV-2 is capable of infecting us year-round, potentially several times per year. It is not seasonal, and it is not a “one and done” infection to which we gain lifelong immunity. Quite the opposite, in fact, as there is increasing evidence that each reinfection is another roll of the dice for experiencing severe acute illness and/or long COVID. The ideal number of times to be infected by the virus is zero, but once is much better than twice, which is better than three times, and so on. In other words, it is very much in the best interest of your health and that of your loved ones to minimize the number of times you are infected.
Reducing the total number of infections is a good thing at the population level as well. Widespread infections may provide some degree of partial, temporary population-level immunity (at least to severe acute COVID), but immunity wanes and SARS-CoV-2 continues to evolve the capacity to escape prior immunity. More virus means more replication means more mutation means more variant evolution. Our so-called “wall of immunity” has been breached multiple times by new variants and as our immunity waned, and with vaccine rates abysmally low, a reliance on infection-based immunity boosting is a problematic strategy indeed.
Infection with COVID is not a common cold, and there is increasing evidence of cumulative effects on the body of repeated infections rather than each one necessarily becoming more benign. There is also no reason based on evolutionary theory to expect each new variant to be “milder” than the last. Think of infection like automobile accidents: it’s best to avoid them entirely if at all possible (and to use measures like seatbelts and airbags to minimize injury if they do occur), but getting into one is better than getting into two which is far better than getting into five or ten.
It matters which variant is circulating and whether you have existing immunity. We have learned through hard experience that a reliance on “herd immunity” or a “vax and relax” strategy will not provide escape from the COVID quagmire. Immunity achieved through vaccination or -- far less desirable – past infection(s) is partial and temporary as immunity wanes and the virus continues to evolve. Nevertheless, vaccination remains an important tool for preventing the worst acute outcomes of infection, and may significantly reduce the chances of developing long COVID, even if by itself it does not end transmission chains. A large population-based study that was recently published shows that multiple boosters may also substantially reduce the risk of long COVID. Work done by one of us (A.C.) suggests that more frequent boosters may also reduce the risk of infection. At the time of this writing, we are on the third iteration of vaccines against COVID-19, with the most recent targeting the XBB.1.5 (“Kraken”) variant. That variant is no longer circulating in large amounts, but so far it seems that boosting with this updated vaccine provides protection against severe acute illness with infection by newer variants. In short, get boosted – but don’t stop there. You can think of vaccines like airbags – they reduce the chance of experiencing the worst outcome when things go wrong, but avoiding such a situation is greatly preferable.
It matters how long and how often you’re exposed to the virus. The initial number of particles required to initiate an infection is very small — on the order of tens to hundreds (depending on the way this is evaluated, be it through human challenge studies or computational fluid dynamics: see here, here, and here). In practical terms, this means that it can take only minutes to inhale enough virus to be infected. However, being exposed is not the same as being infected. The key is to reduce the risk by reducing both the frequency and duration of exposures. (As an evolutionary aside, the small number of viral copies needed to infect creates a narrow genetic bottleneck for the virus, meaning that of the vast number of viral copies present within a contagious host, only a tiny fraction of them make it into a new host to start the next new infection.)
It matters how much virus you breathe in when you’re exposed. The SARS-CoV-2 virus is airborne, but it doesn’t float on the air as naked virions. Instead, it is carried around in very tiny particles of saliva and mucus — this is one reason that masks block the virus but not respiratory gases (and if it’s an N95-style respirator, there’s some very cool physics involved). We know from clinical characterization, backed up by reverse genetics and computational fluid dynamics (CFD) studies that the initial site of infection are the cells of the nasal cavity (nasopharynx) in most cases — computational fluid dynamics studies point to 2-5μm droplets being the size that is deposited at the nasopharynx.
It matters what you do if you’ve been exposed. It may not take a lot of virus to get things started, but it is also not the case that exposure always means infection. It is not enough for a virus to enter your airway – it also has to take hold by entering your cells, replicating and spreading to new cells, and to grow from an initially (hopefully very small) inoculating population to a full-blown infection involving billions of copies. So, if you think you have a cold, get tested. Even if you test negative the first time, test for a couple of more times, as people often test negative despite having COVID.
It matters what you do if you are infected. Does catching COVID mean you just have to hope for the best or that everyone in your household will now be coming down with infections? No! COVID is not a cold- it’s a car accident. Every bout of COVID is a gamble with your health. There are things you can do concretely to reduce your risk of a negative outcome, and so it’s important to know that you have COVID. We will discuss this more in our next post, coming next week.
So, what can you do?
There are a few simple measures you can take to maximize your chances of riding a COVID wave without getting infected. The basic idea is to reduce overall exposure, minimize the amount of virus in the air, shrink the amount of virus you breathe in, interrupt the virus’s ability to take hold if you breathe it in, and limit viral load and odds of onward transmission if you become infected. Again, the tools available are not all or nothing options – it’s about layering as much protection as possible to minimize risk as much as possible.
Avoid exposure. That especially means avoiding large indoor crowds in poorly ventilated spaces and places where a large number of people are passing through throughout the day. This can be difficult to do when gatherings or travel are unavoidable, but any reduction in high-risk exposure is a good thing. One of us (A.C.) and collaborators asked the question, “how much do you need to shield in order to reduce your risk of infection?” If you’re vaccinated, any time you reduce your contact rate to below 50% of the average contact rate in the population, you will begin to see clear benefits in reduction of risk of infection. A 50% reduction in contact rate might sound like a lot, but it’s really not. Contact rates vary by country, of course, so let’s focus on North America first. A 2007 simulation study based on the city of Portland, Oregon, inferred about 10-20 close contacts per person per day. Most people who live in cities also share air with hundreds of others in a variety of settings. These fleeting interactions also carry some degree of infection risk, although it turns out that the risk does decrease when you’re not in contact with them for as long (either because of the lower dose of infectious particles, or because your immunity does some of the heavy lifting). The other way to reduce exposure is – you guessed it – wearing a mask.
Wear a mask as much as possible when indoors. This is really the one practical and simple thing that you can do to cut your risk down dramatically. For some people, social or work pressure may make this difficult in all settings- but again, it’s not all or nothing. Wearing a mask in most (not all) public settings still dramatically reduces your contact rate, both for close and fleeting contacts. If, during a wave, you limit situations where you’re unmasked indoors to only doing so in the presence of members of your own household, you can expect to drive that contact rate down even further. A well-fitted n95 mask is the ideal- it’s just as available, and marginally more expensive, than the alternatives these days. That said, it’s not all or nothing- studies that did not differentiate between different grades of mask still show that that masking leads to a robust reduction in risk of infection.
Go outside. Transmission can and does occur outdoors, but the risk is dramatically reduced compared with the indoors. It is possible to be infected from passing someone outdoors, but the risk is transient (it peaks within 1-2 seconds outdoors). Holding your breath for 15 seconds when you pass someone on a trail may be enough, according to computational fluid dynamics studies. Wind, humidity, and sunlight also represent factors that affect viral persistence in the air, as you can explore with this calculator. That is, it matters if it is windy and sunny and humid and if you are upwind or downwind. Again, not all or nothing.
Improve indoor air quality: SARS-CoV-2 spreads in aerosols, much like cigarette smoke. A room with an infected person can have airborne viral particles in it that linger for hours after the person has left the room, so it’s important to have ways of filtering the air. A number of studies have shown that improving indoor air quality can have an impact on reducing transmission. This can be accomplished by ventilation (as simple as opening the windows), filtration (using a HEPA filter on your HVAC system or adding portable HEPA filters throughout your home) or treatment. In brief, a useful rule of thumb is that you need at least five air changes per hour to substantially reduce the risk of transmission. Improved air quality works best with other layered mitigation strategies, as this paper from the winter of 2021 maps out. The ‘how to’ aspects of this topic can get quite technical, so here are some helpful online resources to get you started if you’re looking to improve the air quality within your home or workplace.
Use a portable CO2 monitor: When you’re out and about, consider using a portable CO2 monitor to assess your risk. In very basic terms, the CO2 level is a reasonable proxy for how so it’s a reasonable proxy for how well ventilated a space is and gives you an indication of how much of the air you’re breathing was recently present in someone else’s lungs. There are many portable CO2 monitors on the market at various price points, so here are some starting points for you to explore further, if you’re interested. The value of using a portable CO2 monitor increases when you use it to inform your risk mitigation protocols after a high-risk situation.
Look into nasal sprays and mouthwashes. What risk mitigation protocols, you say? In a layered mitigation strategy, it is helpful to have additional layers of protection that extend beyond masking and avoiding crowded spaces indoors, especially during a wave. A number of in vitro and in vivo studies have shown that mouthwashes can reduce viral load, for example, although clinical data on this point is still somewhat limited. There are a number of nasal sprays available, that are typically based on ingredients that are generally regarded as safe (GRAS). Iota-carrageenan is a common ingredient in several of the sprays- a study conducted in Argentina showed an 80% reduction in the relative risk of infection (marginally statistically significant at p=0.03). Another common ingredient in some of the nasal sprays is nitric oxide- two clinical studies (England and India) testing a nitric oxide nasal spray in COVID patients found that the use of the spray leads to a quicker reduction in virus levels compared to placebo. Clearly, more clinical data is needed, and trials are ongoing in some cases. (In general, this will take some Googling and digging through the hyperlinks for you, but we have made our own prophylactic routines, and you have the resources here to evaluate your options, hopefully.)
The take-home message here is: it’s not inevitable that you will take COVID home, even during a major wave. You are not powerless and infection is not unavoidable, even if broader public health efforts to mitigate transmission have fallen by the wayside. Importantly, the tools you need are accessible and are not all-or-nothing. Every layer of protection helps and should be used as much as possible to maximize your odds of making it through a wave uninfected.