As Covid-19 raged through New York and New Jersey in the spring of 2020, some experts expressed cautious hope that summer weather might slow its spread. A few even predicted that the pandemic would mostly vanish by fall. It wasn’t a completely implausible assumption. After all, heat and humidity degrade many viruses, and colds and flu taper off in the summer as people spend more time outdoors. Instead, the virus continued spreading like a prairie fire, steadily moving into areas that had mostly escaped the first wave. Fall brought more bad news. And by the time winter weather set in, a full-blown second wave was cresting in much of the country.

We learned the hard way that Covid-19 does not behave like other, more familiar, respiratory viruses. The hope that it would was just one of several overly optimistic assumptions that have hobbled our response to the pandemic. A bigger mistake was made by public health officials who waited months to warn that the virus might be transmitted through the air, and not just by coughs and runny noses. Officials also put too much faith in the idea that draconian lockdowns of businesses, schools, and other settings would stop the spread. Clearly, the pandemic humbled many experts and exposed weaknesses in our public health institutions. It also dramatically changed many of the fundamentals of American life; the ways we work, socialize, worship, and communicate have all been affected. As the vaccine rollout continues, and the country opens its doors again, some of those changes will be happily forgotten. But others may become permanent fixtures of the American landscape.

In the pandemic’s early months, the World Health Organization, the Centers for Disease Control, and other public health experts maintained that Covid-19 is spread mostly through “close contact” with an infected person. Close contact would include handling items the person might have touched and spending time within an area where you could inhale the “respiratory droplets” that people expel, particularly when they sneeze, cough, or talk. Since most of those fairly large droplets were believed to settle to the ground within about two meters, public health officials repeatedly cited the six-foot rule as the yardstick of safety. Most official messaging focused on sanitizing surfaces and frequent handwashing as the first line of defense.

Almost from the start, though, other experts argued that the virus might stay suspended in the air longer, and travel farther, than the leading health agencies said. Reports from the Diamond Princess cruise ship, a South Korean call center, a Washington State choir rehearsal, and other sources all suggested that contagious people might be able to infect others who were nowhere near them. “In the minds of scientists working on this there’s absolutely no doubt that the virus spreads in the air,” said Lidia Morawska, an aerosol scientist at Australia’s Queensland University of Technology, back in April. “This is a no-brainer.”

Nonetheless, the WHO and other agencies continued downplaying airborne risks even as the virus spread globally. In some cases, public officials went beyond simply admitting that little was known about coronavirus transmission and offered false assurances. “It doesn’t just hang in the air,” New York mayor Bill de Blasio insisted at one press conference. The CDC waited until October to warn the public that the disease might travel through the air “in limited, uncommon circumstances.” Today we know that the airborne route is one of the most common means of Covid-19 transmission, especially in “super-spreader” events in which one person infects many others.

The failure of public officials to acknowledge the risks of airborne transmission meant that our main strategies for avoiding Covid-19 had been inadequate for months. The experts who said, “Just wash your hands!” were wrong. Handwashing, while necessary, clearly isn’t sufficient. And the six-foot rule was little more than an educated guess. Meanwhile, businesses and institutions busied themselves with what some call “sanitation theater,” while neglecting the invisible risks that were very much hanging in the air.

If the virus can stay airborne for minutes or hours, that means that the most dangerous environments are enclosed spaces where groups of people share the same air for long periods. Both hot and cold weather, which drive people indoors, exacerbate the problem. Harvard Medical School professor Edward Nardell, an expert on infectious diseases and environmental health, noted the correlation before most. “The states that, in June, are already using a lot of air conditioning because of high temperatures are also the places where there’s been greater increases in spread of Covid-19,” he said last summer. Nonetheless, many officials, perhaps eager to appear decisive, focused on restricting outdoor activities, which actually pose relatively low risks. States and localities closed parks, beaches, and playgrounds. Police were dispatched to arrest unauthorized sunbathers, joggers, and, in Malibu, California, a solitary paddleboarder.

One key exception to the stay-at-home directives came during last summer’s Black Lives Matter protests. After months of stressing the risks of public gatherings, many officials applauded the demonstrations. A group of 1,200 health experts and “community stakeholders” signed an open letter encouraging more protests, on the grounds that “white supremacy is a lethal public health issue.” Many Americans bristled at the idea that Covid restrictions could suddenly be waived for the right political cause. The messages from public health officials were already muddled. Now, many perceived them as hypocritical, to boot. The tolerance for lockdowns and mask wearing, already wavering, began to collapse in many communities.

Covid’s spread around the country also punctured another assumption about the virus. Early in the crisis, it was widely believed that high population densities made cities like New York particularly vulnerable. Even New York governor Andrew Cuomo concurred. But as cases flared in the Sunbelt’s suburban sprawl, and then even in such thinly populated states as North Dakota, it became clear that urban density wasn’t the culprit. “Covid-19 isn’t a problem of square kilometers, but one of square meters,” says science writer Adam Rogers. The most dangerous environments aren’t city sidewalks, or even subways, but those where people closely interact in tight indoor quarters: nursing homes, prisons, meatpacking plants, and, of course, private homes. So the problem isn’t how many buildings a city has; it’s how many people are crammed into each building. This is good news for New York. If indoor spaces can be rendered safer, New Yorkers will be at no more risk of exposure than denizens of Nantucket, Natchez, or Napa.

Despite its world-famous urban density, Japan has had success against the virus without a wholesale shutdown of society. Instead, health officials there focus on helping people avoid what they call the Three Cs: closed environments with little ventilation; crowded places; and close-contact interactions between people. Since people emit far more virus-laden droplets when they’re talking or singing, those activities raise the risk. So does the amount of time a person spends in these settings, since the body can accumulate virus particles gradually. Japan’s public health policy focused on reducing indoor density and improving ventilation. Many Japanese were already in the habit of wearing face coverings during flu season, so persuading the public to mask up was straightforward. As a result of those fairly modest interventions, Japan was able to keep most businesses and schools open.

The U.S. and other Western countries have moved far too slowly in emulating Japan’s example. While lockdowns should theoretically suppress the spread of Covid-19, the evidence for their effectiveness isn’t ironclad. For example, California, which imposed some of the country’s tightest restrictions, nonetheless faced a devastating second wave in the early winter of 2020–21. And lockdowns come with high social and economic costs, especially for lower-income families.

The shockingly swift development and approval of two Covid-19 vaccines provided hope for faster, safer reopening of U.S. society. The initial rollout of the vaccines was rocky, however. Some critics contended that the Trump administration’s Operation Warp Speed had failed to plan adequately for the “last mile” of delivery, i.e., actually getting shots into arms. Federal officials left those details mostly up to the states, which varied widely in competence. High-tech California struggled, while some rural states, including West Virginia and Alaska, moved with alacrity. (In Alaska, some doses reached tribal communities by dogsled.) Guidance from the CDC was, once again, muddy. At first, the agency floated a complicated plan that stressed “social justice” over speed. The early weeks of the rollout were hobbled by confusion and controversy over which groups to inoculate first.

Despite the speed bumps, the U.S. is still vaccinating its citizens at a rate faster than all but a handful of countries around the world. And, with more vaccines in the pipeline, that rate will improve rapidly. “A transition to normalcy will occur when Covid-19 mortality falls and the disease is de-exceptionalized in society,” analysts at McKinsey & Company predict. That process will begin in the second quarter of 2021, they say. That doesn’t mean that Covid-19 will disappear entirely this year but rather that it will become “part of the baseline disease burden in society,” much like the flu.

Meanwhile, the push to reopen businesses, schools, and other institutions continues, and can’t wait for every last person to be vaccinated. The prescription for reopening relies on three main strategies: reducing the density of people in indoor spaces; reducing the amount of airborne virus circulating in those environments; and limiting the number of shared surfaces that people need to touch over the course of a day. Some of these changes are as easy as installing hands-free soap dispensers. Others will require architectural overhauls of indoor spaces. And some will entail long-term changes in how Americans work and socialize.

An employee stands on a social-distance marker in an office elevator. (DYLAN HOLLINGSWORTH/BLOOMBERG/GETTY IMAGES)
An employee stands on a social-distance marker in an office elevator. (DYLAN HOLLINGSWORTH/BLOOMBERG/GETTY IMAGES)

The easiest strategy for reducing people’s exposure is simply to put more space between them. This not only reduces the chance of direct contact with a coronavirus carrier but also means that fewer people are breathing the same stuffy air. To some extent, this is happening already. According to a Stanford University study, 42 percent of U.S. workers began working from home during the pandemic. A meaningful share of those will never return to in-office work. A Harvard study suggests that roughly 15 percent of onetime office workers will continue to work from home. “The notion of putting 7,000 people in a building may be a thing of the past,” Barclays’ chief executive, Jes Staley, has said.

Global architecture firm Gensler forecasts that the office of the future “will no longer be a single physical place, but a collection of connected physical and digital spaces.” Workers at home will collaborate with their in-office colleagues through seamless interfaces. Gensler predicts that workers will tend to stay home for “intense heads-down work” and use days in the office “to be with our teams, colleagues, and clients in person.” Fewer bodies in the office might allow a welcome reversal of a long-term trend. The amount of space devoted to individual workers has plummeted in recent years as businesses embraced jam-packed “open-plan” offices. Though C-suite executives love these money-saving layouts, a 2018 Harvard Business School study showed that open plans actually reduce collaboration. Now, with fewer people working on site, businesses can rejigger those floor plans to allow more partitions, more space—and more breathing room—for workers.

Nearly a year into the pandemic, school administrators are still wrestling with the question of how many students can safely share a classroom—or whether they should be in school at all. Teachers’ unions have fought hard against reopening in many communities, while private schools have been much more likely to have students in classrooms. While trepidation on the part of teachers is understandable, studies show that classrooms are surprisingly safe environments. A recent report in the Journal of American Pediatrics tracked Covid-19 rates in 11 North Carolina school districts as they returned to in-class operation. That investigation didn’t find a single case of child-to-adult transmission in a population of 100,000 students and staff over the course of nine weeks.

Public school staffers in New York, Chicago, and other regions have been assigned priority vaccination status. Nonetheless, resistance to in-person teaching remains high. In late January, members of the Chicago Teachers Union voted not to go back to classrooms just two days before 10,000 elementary students were scheduled to return. In Virginia’s Fairfax County, a union president demanded that teachers shouldn’t be required to return until students are vaccinated as well. Given that neither available vaccine has yet been approved for children under the age of 16, that demand could mean that some Virginia students wouldn’t see the inside of a classroom for close to two years. It seems unlikely that parents will stand for that.

Reducing crowding in other environments, such as restaurants, religious meeting places, and entertainment venues is another challenge. New York’s Broadway theaters—with their troupes of vigorous singers and tightly packed audiences—face perhaps the toughest road. (See “Broadway’s Dark Year.”) Estimates for when theaters could reopen have been pushed back several times. Dr. Anthony Fauci recently told a performing-arts group that he believes that Broadway theaters will be able to reopen at “near-capacity” in the fall of 2021. City restaurants—those that have survived, at least—were allowed to reopen at 25 percent capacity in mid-February. Restaurants were implicated in some of the earliest “super-spreader” research. Still, it remains unclear how big a factor they have been in spreading Covid-19 in the United States. In New York, just 1.4 percent of cases have been linked to restaurants and bars, according to data released by Governor Andrew Cuomo in December. (Household or social gatherings accounted for 74 percent of New York cases.) On the other hand, several studies conclude that public dining poses a moderate threat, at least if we assume that restaurants will quickly return to pre-pandemic capacity.

That’s unlikely, of course. People have become wary of crowded indoor spaces regardless of government restrictions. Online reservation data show that, as the pandemic escalated, diners started avoiding restaurants even before lockdown orders were issued. It appears that a certain portion of the public is likely to remain cautious about venturing into crowded venues—at least until a larger percentage of the population is vaccinated. That is bad economic news for the restaurant industry, but it also means that many establishments will be able to reopen at lower density and with safety protocols in place. And restaurants—like office buildings, schools, and other settings—can make their spaces safer by improving ventilation.

Since Covid-19 transmission depends significantly on the number of viral particles circulating in an enclosed space, anything that reduces that quantity lowers the risk. Building managers have three main options: they can dilute the inside air mass by bringing in more fresh air; they can trap viruses with filters; or they can kill airborne viruses with some type of germicide. The most effective defense combines all three. The easiest way to dilute interior air is simply to open a window, but that’s not usually possible in modern office buildings. For decades, building engineers have worked to improve energy efficiency by limiting the amount of outside air admitted into the structure. Now they’re being told to forget about efficiency. A safer workspace requires bringing in as much outside air as possible and running HVAC systems around the clock to keep fresh air circulating. McKinsey and others also advise building managers to install carbon-dioxide detectors to monitor air quality. Since people exhale CO2 with every breath, an elevated CO2 reading indicates that indoor air is not being replenished fast enough.

Cranking ventilation systems up to full blast can create a new set of problems, however. One of the most discussed studies of Covid-19 transmission traced a cluster of cases caused by a single virus carrier in a Wuhan, China, restaurant. Researchers concluded that the restaurant’s air-conditioning system spread the virus to patrons at other tables. “The key factor for infection was the direction of the airflow,” the authors said. In this case, the moving air simply distributed respiratory droplets much farther than the theoretical two-meter limit.

But there’s another, more insidious, way that air conditioning can spread coronavirus. When first expelled, respiratory droplets are fairly large—roughly five to ten or more microns—and therefore heavy enough to settle quickly. The droplets encase the coronavirus in tiny globs of mucus and saliva, but they begin drying out almost instantly, especially in the low humidity afforded by air conditioning. In less than a second, they can shrink to a tiny fraction of their original size. Particles smaller than five microns are usually classed as “aerosols,” a word that sends chills down the spines of infectious-disease experts (and one that the WHO and CDC largely avoided for months). These nearly weightless “desiccated particles” can stay airborne for half an hour or more, viral payloads intact.

Even after these desiccated globs settle out of the air, they still pose some risk. In an ominous report, scientists specializing in disease transmission in the “built environment” warned that desiccated particles can be “re-suspended” by ventilation systems, or even via the subtle turbulence caused by “foot fall, walking, and thermal plumes from warm human bodies.” A McKinsey report advises building managers to avoid overly aggressive ventilation by installing variable-speed fans and sophisticated systems to measure airflow. Ideally, offices would have a smooth, or “laminar,” ceiling-to-floor airflow, though that’s not feasible for most. (The ceiling-to-floor airflow pattern used on passenger planes might be one reason that there have been surprisingly few Covid cases linked to air travel.)

Perhaps the scariest spot for returning workers will be the office restroom. Here, too, airborne germs are a risk, and not just those that people exhale. (Yes, this is just as disgusting as it sounds.) Modern toilets have been proven to “aerosolize” the contents of the bowl, sending up a three-foot “toilet plume.” The droplets in these plumes dry out and travel through the air just like those from a sneeze and are known to transport viruses and bacteria. Coronavirus is present in human feces—though, fortunately, there haven’t been any confirmed cases of Covid-19 being transmitted by this route. But just in case, an association of HVAC experts advises that restroom exhaust fans “should always be kept on 24/7.”

Then there’s air filtration: the HVAC systems in commercial buildings normally include air filters, but most are rated at a Minimum Efficiency Reporting Value (MERV) of 12 or less. These can remove most particles greater than one micron, but more intense filtration is needed to handle smaller desiccated droplets. Experts generally recommend filter systems of MERV 13 or above. At the upper end of the MERV scale lie HEPA (high-efficiency particulate air) filters. These are rated to remove virtually all particles of 0.3 microns, though studies show that they handle both larger and smaller particles extremely well. HEPA filters are commonly used in hospitals and other specialized settings. But they require much higher air pressure to operate. Retrofitting conventional HVAC systems to handle these higher levels of filtration will be a challenge for many building owners.

For small spaces, such as individual offices or barbershops, stand-alone room air purifiers provide a good ad hoc option. While there’s not much research on whether these consumer-grade HEPA filters reduce coronavirus transmission, experts believe that they can make a big difference, especially in settings that lack state-of-the-art HVAC systems.

Finally, airborne viruses can be killed before they infect anyone. People have been using germicidal lamps for over a century to fight tuberculosis and other diseases. Ultraviolet light in the shorter wavelengths, known as UVC, has been shown to kill many viruses. Exposure to UVC light is potentially damaging to human skin and eyes, however, so it’s best used in indirect applications and installed by professionals. Some ventilation systems already include UVC stages. Another approach uses UVC lights installed near the ceiling, where they don’t shine on the people below but can kill virus particles that waft up on air currents.

Employees wear protective masks at a socially distanced office meeting. (DYLAN HOLLINGSWORTH/BLOOMBERG/GETTY IMAGES)
Employees wear protective masks at a socially distanced office meeting. (DYLAN HOLLINGSWORTH/BLOOMBERG/GETTY IMAGES)

As attention has shifted to the airborne transmission of Covid-19, it’s important to remember that the disease can still travel by the surface-to-hand-to-face route. Last summer, at least 19 people contracted the illness after attending an Ohio county fair, an outdoor setting where airborne transmission seems less likely. Shared ketchup and mustard bottles are considered a probable culprit. Such shared surfaces abound in indoor settings. Think of the office coffeemaker or vending machine, not to mention door handles and elevator buttons. Business owners and building managers are now working to minimize as much of that physical contact as possible.

Last year, Cushman & Wakefield, the property-management giant, moved nearly 1 million workers back into office buildings that it helps manage in China. Returning a workforce to an office in the Covid era is a process “without precedent,” the company says in a report. In addition to new protocols for sanitation, the firm advises that unnecessary doors, shared phones, and even whiteboard markers be removed. Of course, workers will need training in the new procedures. The company suggests appointing “Covid-19 block captains” and “quarantine marshals.”

Gensler, the architecture firm, believes that many of these changes will be permanent. One report envisions a “touchless” journey from building entryway to desk: workers would breeze through security, their identities confirmed via facial recognition and health checks performed remotely; preprogrammed elevators would whisk them to their floors, where doors swing open in anticipation. The building-security system would perform “continuous scanning of our patterns and preferences through the spaces we navigate.” It all sounds a tad Orwellian. Buildings can be made much healthier without requiring ubiquitous surveillance from a corporate Big Brother.

Widespread vaccination will gradually reduce Covid paranoia. By next year, some accommodations now being made to cope with the disease will feel like overkill. But in a world that is increasingly tightly coupled, Covid-19 will not be the last pandemic we face. Nor even the worst, quite possibly. With improved treatments, the Covid-19 case fatality rate (for confirmed cases) is now well below 2 percent in the United States. Imagine the horror if Covid killed off more than 10 percent of its victims, as SARS did. As this pandemic wanes, government leaders, public health officials, and even ordinary citizens will remain more cognizant of the potential for another virus to sweep through our society. Many recent infrastructure changes—such as lower-density offices and improved ventilation—will remain in effect. And some changes in behavior—such as our reluctance to shake hands or our wariness of crowded spaces—will linger in the back of our minds, ready to revive at the first sign of a strange new malady.

Perhaps next time, with a little more planning and a little better luck, we’ll be ready.

Top Photo: A restaurant owner looks at her new air purifier in preparation for the reopening of indoor dining in the city last autumn. (KATHY WILLENS/AP PHOTO)


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