Editor’s note: This story launches “New York City Reborn,” an ongoing series on how the city can come back from the crises of 2020.
As the coronavirus raged through New York and New Jersey in March and April, some experts expressed cautious hope that summer weather might slow its spread. It was a reasonable assumption. After all, heat and humidity degrade many viruses, and colds and flu taper off in the summer as people spend more time outdoors. In the heat of midsummer, however, those hopes were dashed. Covid-19 cases surged in many states, though, thankfully, death rates remained comparatively low, and the outbreaks are subsiding in most areas. The country’s hottest regions, including Florida, Arizona, and Southern California experienced the biggest surges in cases.
Covid-19’s summer rebound shows that two early assumptions about how the disease spreads were dangerously faulty. One concerned how the virus behaves; the other, how people behave. Both have serious implications for how we minimize coronavirus risks even as we continue reopening businesses, schools, churches, and other institutions.
In the pandemic’s early months, the World Health Organization, the Centers for Disease Control, and others 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, and other sources all suggested that contagious people might be able to infect others who were nowhere near them—perhaps even in other rooms.
“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.” Only recently have the WHO and CDC softened their positions to warn that airborne transmission is a risk as well. In effect, that meant our main strategies for avoiding Covid-19 had been inadequate for months. The experts who said, “Just wash your hands!” back in February were wrong. Handwashing, while necessary, clearly isn’t sufficient. And the six-foot rule was little more than an educated guess.
The other flawed assumption was the hope that people would spend enough time outdoors to slow the spread of the virus. Maybe that was possible in the more temperate regions of the U.S., but did anybody really think that residents of Florida and Arizona were going to spend hours in the summer sun each day? Harvard Medical School professor Edward Nardell, an expert on infectious diseases and environmental health, believes that air conditioning played a key role in the rebound. “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 recently said.
The summer surge in Covid cases revealed how those two flawed assumptions overlapped to prolong the crisis. If the virus can hang in the air for minutes or longer, that means that the most dangerous environments are enclosed spaces where groups of people share the same air. And when people retreat indoors during hot weather, it means that, rather than providing a safety valve, summer merely prolonged the pandemic. (Of course, the surge was also preceded by the mass protests in reaction to the George Floyd killing. Some media outlets were quick to downplay any connection. And the rate of transmission appears to be much lower outdoors. Still, the question of how much these large gatherings might have driven up Covid-19 cases remains conspicuously under-researched.) Whatever the main driver of transmission, summer failed to tamp down the spread. Fall and winter promise no respite, since that’s when most Americans spend even more time indoors.
The summer Covid spike also punctured a third assumption. 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 Sun Belt’s suburban sprawl, it became clear that urban density wasn’t the culprit. “Covid-19 isn’t a problem of square kilometers, but one of square meters,” writes 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, bars, and restaurants. 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. In fact, given how many residents have already recovered from Covid-19—thus reducing the pool of people capable of catching and spreading it¬—New York today might be one of the country’s safest locales.
“Covid-19 is an indoor disease,” writes British physician Jonathan Fluxman. Understanding the nuances of how coronavirus spreads indoors will be key to reopening our institutions and economy safely. 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.
Of course, people “closely interacting in crowded, indoor spaces” describes much of what happens in offices, schools, churches, restaurants, and entertainment venues. Those spaces are designed to facilitate close interaction—and therein lies the biggest challenge to reopening efforts. Everyone responsible for running these shared environments is trying to figure out what to do next. A middle school principal I know is spending her summer poring over floor plans, trying to calculate how many desks can fit in a classroom with six feet of separation. Building managers are researching HEPA filters and “touch-less” entryways. Restaurant owners are constructing partitions between tables.
The ultimate Covid defense, of course, would be an effective vaccine. Several current trials show promise, but there are no guarantees. And even if a safe and effective vaccine is found, it might take a year or more before a sufficient portion of the U.S. population is vaccinated. More widespread and frequent testing would also ease reopening. The NBA and other sports leagues are requiring that players be tested regularly, and that they stay in protective “bubbles.” Some colleges and other institutions are pursuing similar approaches. Harvard, for example, plans to test all students every three days this coming semester. For such a program to work, we need ample testing capacity and fast turnaround of results, something still lacking in parts of the country.
The FDA recently announced that it will allow testing of “pooled samples.” Under this protocol, a small group—say, all the students on one dormitory floor—could have their test swabs combined in a single test run. If a batch tests positive, all those students then go into quarantine and get retested individually. Among presumably healthy populations, this approach drastically increases the number of people who can be tested regularly. However, in a move one expert calls “inexplicable and irresponsible,” the CDC recently reiterated its opposition to testing asymptomatic students or employees returning to school campuses. (This isn’t the first time that the CDC has dragged its feet on supporting simple steps that might reduce Covid risk.)
Fortunately, institutions don’t have to wait for a vaccine or rapid-fire testing to reopen with reasonable safety. Groups of architects, engineers, infectious-disease experts, and others are crafting recommendations for getting people back to work, school, and play. Their solutions take the risks of airborne coronavirus seriously. But these experts don’t assume that the continued presence of a contagious disease means that the country must stay on permanent lockdown.
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. The changes that business owners, school officials, and others implement in the next few months will shape how key parts of American society function for years to come.
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 recirculated air. To some extent, this is happening already. According to a Stanford University study, 42 percent of U.S workers have been 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. Many businesses plan to stagger their workers’ office days, allowing most to stay home one or two days a week. “The notion of putting 7,000 people in a building may be a thing of the past,” Barclays’ chief executive Jes Staley said recently.
Fewer bodies in the office would be 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. C-suite executives love these money-saving layouts and often repeat the claim that the lack of partitions enhances teamwork. This has always been nonsense; a 2018 Harvard Business School study showed that open plans actually reduce collaboration. Inc. magazine calls the open office “the dumbest management fad of all time.” Now, with fewer people working on site, businesses can rejigger those detested floor plans to allow more partitions, more space—and more breathing room—for workers.
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.”
Plans for how to reopen colleges and K-12 schools are a mishmash. Some schools are aiming for full attendance while others will remain online-only, but many others are exploring hybrid strategies similar to those that businesses are pursuing. New York mayor Bill de Blasio has announced a plan that brings students back to school two to three days a week. But the mayor insists that students won’t be attending full-time any time soon. “The day we get the vaccine is the day we’ll really go to full, five-days-a-week normal instruction,” he told MSNBC’s Morning Joe.
It’s not clear that such extreme caution is called for, at least not in New York, where the rate of positive coronavirus tests is now under 1 percent. A French study found that school children don’t appear to spread the infection to teachers or classmates. On the other hand, a study in South Korea suggested that children over age ten do transmit the virus readily, though that conclusion quickly came under fire from other researchers. In any case, many experts argue that the harms of keeping children out of school outweigh the risks of Covid in the classroom. The American Academy of Pediatrics advises that “all policy considerations for the coming school year should start with the goal of having students physically present in school.”
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. They are not expected to reopen until January 2021, at the earliest. For restaurants and other small venues, though, the problem of crowding might partially solve itself. Online reservation data shows that, as the pandemic escalated, diners started avoiding restaurants even before lockdown orders were issued. When cases surged in the South and West, the number of people dining out plunged again. It appears that a certain portion of the public is likely to remain cautious about venturing into crowded spaces indefinitely. This is terrible news for restaurants and entertainment venues, but it’s also an opportunity to offer more space to the patrons who do show up.
Many business owners are finding innovative ways to keep their businesses going, even with distancing protocols in place. Kate Davies operates YO BK, a pair of hot-yoga studios in Brooklyn. “The day after we closed our studios we started live online classes,” she says. Since then, she has added outdoor classes, using rooftop spaces at nearby hotels (heat and humidity aren’t a deal breaker for hot-yoga fans). When indoor classes resume at her studio, “things will be very different,” she says. Instead of 40 people in a class, sessions will be limited to 10. “We’ll have to manage crowding, even in our lobby area” she says. “We’ll stagger classes and ask people to show up just before class and leave right after.” Across the country, businesses from hair salons to dentist offices are making similar adjustments.
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. All that takes a toll on energy usage. One study found that pandemic protocols boosted HVAC costs by 36 percent.
And cranking ventilation systems up to full blast creates a new set of problems. 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 5 to 10 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 5 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,” or “droplet nuclei,” 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 & Company report advises building managers to avoid overly aggressive ventilation by installing variable-speed fans and more 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, especially the high-pressure models used in public buildings, 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. In fact, scientists are testing municipal wastewater as a kind of early-warning system for Covid-19 outbreaks. Fortunately, there haven’t been any confirmed cases of Covid-19 being transmitted by this route. However, in 2003, 300 residents of a Hong Kong apartment building were believed to have been infected with the SARS coronavirus via faulty plumbing. An association of HVAC experts advises that restroom exhaust fans “should always be kept on 24/7.” Experts also recommend keeping toilet lids closed while flushing—a challenge in most public or office restrooms, which typically don’t have lids.
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 over 1 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 a NASA study suggests that they work with particles as small as 0.01 microns. That’s less than a tenth the size of a single coronavirus particle.
HEPA filters are commonly used in hospitals, clean rooms, and other demanding 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. New York governor Andrew Cuomo recently announced that retail malls in the state will have to install HEPA systems before they can reopen. (After some pushback from mall owners, the governor’s office rolled back the requirement to a more feasible level of filtration.)
For small spaces, such as individual offices or barber shops, standalone room air purifiers might be a sensible option. While there’s no specific research on whether these consumer-grade HEPA filters reduce coronavirus transmission, experts believe that they probably help. (People using such filters should be careful that they aren’t employing a high fan setting that might stir up more particles.)
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. Extended exposure to UVC light is potentially damaging to human skin and eyes, however, so it’s best used in indirect applications. Some ventilation systems already include UV stages. Another system uses UV 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.
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. In late June, 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 coffee maker 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.
Cushman & Wakefield, the property-management giant, recently moved nearly 1 million workers back into office buildings 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 new 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.” The sensors in each space would “know that it’s you,” adjusting everything from desk height to air temperature to your liking.
It all sounds a tad Orwellian. Buildings can be made much healthier without requiring ubiquitous surveillance from a corporate Big Brother. In fact, some of today’s measures to improve indoor health might turn out to be overkill. Will Covid-19 keep coming back in waves? Or will it settle into the background, a serious illness that needs to be monitored, but not an existential threat? We really won’t know until society is back to work and our routines are mostly back to normal. Meantime, making interior spaces safe is only half the battle. It is just as important to make people feel safe. If that requires having more open windows and fewer shared ketchup bottles, less-crowded bars and restaurants, and working from home a few days a week, the tradeoff could be worth it.
Photo by Stephanie Keith/Getty Images