Mind Your Aerosols…and Ambivalence
Maneuvering through pandemic existence, with a heightened sense of risk, we immerse ourselves in an elaborate calculation: minimizing exposure and spread of COVID-19. Those with the luxury of staying home have a low chance of contracting the novel coronavirus, in stark contrast to front-line health workers and many other essential people that enable large swaths of the population to shelter in place.
In the U.S., phased re-openings have brought correspondingly higher rates of infection, apparent in real-time data and elaborately forecasted for the next several months. Global organizations, such as the Institute for Health Metrics and Evaluation (IHME) and Our World in Data (OWID), track and predict collective data, while state, county and city health departments handle raw data with expanded testing, contact tracing, and reporting. The zoomed-out lens of statistical data, and modeling for the future, isn’t nearly as valuable without accurate individual data over time, where local expertise holds the critical microscope over action on the ground.
Health guidelines have not been universally followed, and this is distressingly apparent in total per capita infection rates reported by OWID. For comparison to the U.S., I chose four other countries where case counts began to climb within a week or two of each other: France, Germany, Sweden and Iran. For this group of countries, the first half of April showed similar rates of infection: 300-800/million on April 1, increasing to 900-1800/m by April 15. As of June 19, the U.S. is over 6600/m, and all except Sweden (5500/m) are in the 2000s.
If we look at total per capita death rates for the same countries, Germany and Iran are the lowest (≈100/million), Sweden and France are highest (450-500/m), and the U.S. is currently at 350/m. France shows a high number of deaths for a relatively low number of cases, attributed to delayed government response. Further, U.S. infection and death rate is only somewhat lower than Sweden, which kept most businesses open and implemented little lockdown, relying instead on high levels of testing, tracing, voluntary distancing and isolation for vulnerable populations. Sweden also experienced a recent spike in nursing home deaths. The U.S. was delayed in its measures, with a weak federal response, and state-specific stay-home orders combined with the other elements were destined to be patchy and inconsistent: a hack job.
And, while the per capita infections and deaths help put the U.S. data into context, it is no less distressing that IHME forecasting predicts the staggering U.S. death count of ≈100k to double by October. Out of the entire population, the U.S. has had 0.6% confirmed infections. The number of actual infections is higher due to the untested and asymptomatic. Based on antibody testing, Sweden estimates 7.3%, and New York City 12.3% total infections, and we are far from herd immunity. With emerging upticks in Africa, South America, and South Asia, globally, we’re in for a long haul.
Zooming back to the individual microcosm: leaving home increases potential exposure, and staying home reduces it. Every single activity involving other people is a qualitative calculation, posing level of risk against benefit. Outdoor reduces risk, but more people in close distance increases it. Anytime a new person enters the home, there is increased risk to all residents, since a small number of breath aerosols circulate in HVAC ducts. Indoor events carry increased risk in line with the number of people and proximity.
But even before the pandemic, all activity carried risk. Life is a series of decisions based on risk, of which there are many categories, including the health risk now front and center. For example, driving a car to work carries with the corresponding probability of a car accident. We choose to drive because of the value (or necessity) of work. The benefit outweighs the risk, therefore we drive.
With coronavirus, certain activities might not be worth the health risk. For example, a quick stop at the convenience store to satisfy my candy bar craving is not likely to happen. This is now a low-priority activity, given the main variables related to COVID: the number of people we come into contact with, indoors vs. outdoors, time of exposure, and the major unknown quantity of other people adhering (or not) to health guidelines. We’re armed with information before venturing out, but only to a certain degree – cultivating feelings of groundlessness, restlessness, perhaps even helplessness, and oh, so many lessness-es. The heightened uncertainty is both short and long-term. However, while we can’t predict a car accident, the way we drive can absolutely lower those chances. With relatively few mandated guidelines in much of the U.S., individuals bear more responsibility and are called to carry the batons for the community.
Perhaps the science of uncertainty can help reassure our perceived lessness. Quantum physics helps us understand phenomena that can’t be explained with classical physics. As matter approaches sizes on the atomic scale, we lose measurement capabilities with respect to two variables: location and speed. This loss of information is the Heisenberg Uncertainty Principle, stating that if we want to know the location or speed with a high degree of accuracy, we lose information about the other quantity.
In describing this further, I’ll use a ping pong ball to symbolize a tiny particle. In classical physics, we can measure, simultaneously, the exact location and speed of the ping pong ball. The key word is simultaneously: with the right equipment, both can be measured, accurately. In the quantum world, for our tiny particle, we can’t measure one without losing information about the other. The attempt to measure these quantities at the same time is riddled with uncertainty. If ping pong balls acted like atoms, exact measurement of the ball’s location would prevent us from knowing its exact speed. If we, instead, reign in on the speed, we’re no longer sure of its location. This Heisenberg Uncertainty Principle has spawned bizarre thought experiments such as Schrödinger’s Cat, which considers a cat trapped inside a box that is both dead and alive. Until we open the box, we don’t know. In quantum physics, we grapple with the idea that small particles, like electrons, embody multiple states until all of those realities collapse into a measurement. Creative extension of these ideas into our choices and life meaning are explored in weird, fun films like What The Bleep Do We Know?
The Heisenberg Principle is one of the reasons quantum physics works with probabilities over set quantities. Because we are limited in how much we can know at one time, we compromise by knowing location and speed to a large degree: we mostly know, but don’t exactly know.
Coronavirus aerosols are many times larger than atoms, so they are not subject to the Uncertainty Principle. Classical physics has us covered with the ability to know something about their size and ability to travel. We’re all familiar with sneeze/cough droplets; the larger ones are maybe a millimeter, mixed with a bunch of smaller droplets as small as 1/100 of a millimeter, or 10 microns. The small droplets become aerosols at around half that size down to about 1 micron. Now take that 1-micron aerosol and pretend it’s a giant boulder: an atom would be like a tiny grain of sand, and an electron is 1/10,000 smaller than that. Coronaviruses aerosolized in water casings might seem mysterious, but from the standpoint of an atom, they are giant ping pong balls. The bigger droplets succumb to gravity quickly, but are viable on surfaces, and the smaller droplets and aerosols can float around longer.
In this land of probability, a main feature of the quantum world, we can better equip ourselves to manage the global pandemic with enhanced awareness of what’s in the air. Droplets and aerosols are as innocuous as the oxygen we breathe. Without realizing it, we’re applying probabilities—risk statistics— to ordinary life with one key piece of knowledge: the virus is close to its host. With widespread community transmission, augmented by presymptomatic and apparent asymptomatic spread, invisible aerosols as small as one micron (1/1000 of a millimeter) are understood to be prevalent in spread. Of further concern is evidence of travel through ventilation systems and distances more than a few feet, coupled with viability on certain surfaces for a few days.
In the absence of complete isolation, we all have a nonzero chance of exposure to this virus. Our actions dictate the level of risk, with many more than just two variables: number of people, distance, location, and personal hygiene. Ultimately, all these variables can be collapsed into two: what we do (known), and what others do (unknown). This is both empowering and frightening, inducing more lessness.
Let’s revisit the U.S. per capita death rate, currently at 350/million: this is two orders of magnitude higher than South Korea, New Zealand, and Taiwan, where per capita deaths are in the single digits/million. What do the low-death-rate countries have in common? New Zealand, with tight lockdown measures and clear leadership, gained control early and masterfully – and a low population density couldn’t hurt (50/square mile compared to Taiwan/South Korea 1700 and 1300, respectively). Taiwan stepped up production of face masks by early March, eventually donating millions to other countries. South Korea, while currently facing a second wave, uses a system of extensive testing and contact tracing. Further, previous experience with SARS and MERS make Taiwan and South Korea seasoned experts, with general populations already accustomed to face masks. With respect to the U.S., two features weakened its handling of this pandemic: inadequate, inconsistent federal leadership and a population that hasn’t been affected by a pandemic in about 100 years.
A third weakness lies in American attitudes towards freedom. The U.S. doesn’t have a critical mass of people who are willing to simply follow health guidelines. Enough people are skeptical of urgent guidelines or mandates in the name of public health, citing government overreach, the most vocal carrying an almost sanctimonious privilege of not being required to wear a mask in public. The less vocal noncompliant are no less privileged, but for the apparent freedom to not follow guidelines, there is a steep price: more illness and fatalities, extended lockdowns, and worse economic damage.
Face masks offer protection in conjunction with thorough handwashing, regular disinfection of high-use surfaces, and keeping physical distance. Contrary to popular graphics circulating through social media, there are no specific probabilities for rates of transmission with and without masks. However, a recent study by UK researchers (summarized here) discusses widespread mask usage as extraordinarily effective at lowering the rate of transmission (reproduction number) to below 1, corresponding to one person infecting less than one other person. For countries with few resources, mask usage will be heavily relied upon as a cheap and effective method of slowing spread. Another article, more focused on airborne transmission, showed that mandatory mask usage had the largest effect on decrease of cases.
Let’s consider two kinds of freedom. There is the freedom guaranteed by the U.S. Constitution, and then there’s Freedom: personal ego entrenched within Constitution-defined freedom. The former freedom is a noun, inherent to our residency; the latter is a learned attitude, inherent to science contrarianism, that takes many forms: anti-vaxxers, climate change deniers, and now anti-maskers. Subtly, but powerfully, the latter includes people who quietly decide not to wear masks, but wouldn’t dream of taking it as far as the Statehouse.
These warped attitudes towards public health really screws around with probabilities. As an individual, you can be as careful as possible, but then walk into a box store where only 1/3 of the customers are wearing masks. People who more carefully consider their responsibly are shrouded by enough of the careless Free. Ego-centered Freedom literally endangers frontline health, grocery, restaurant, delivery and other workers that regularly interact with people as a workplace requirement. This population tends to be low-income, uninsured, underprotected, underpaid, immigrant and of color: systematically lacking full access to the benefits of guaranteed freedom. The Freedom also increases risk for those who are older or have underlying cardiovascular, pulmonary or diabetic conditions. These populations…they are us. While wisdom tells us we never have control over others: America, we can do better. We can do better by the physically vulnerable. We can do better by the socioeconomically disadvantaged. We can do better by the systematically oppressed. We can do better as examples for others. Better by us.
In the end, each of us might or might not contract COVID-19; we won’t know for sure until we become ill, discover antibodies, or the virus is eradicated. Like the measurement of an atom’s location in quantum physics, having one of many possibilities until measurement, the time we’re uninfected is mired in uncertainty. When we interact with others, there’s a probability of picking up viral particles – but even then, we don’t become infected below a certain threshold of viral nuclei. The potential risk decreases with low numbers of people, outdoors, long distances and short times. Minimizing our exposure probability while loosening our tight hold on certainty is the best we can do: these are the critical variables to manage within this new pandemic reality.