Health-care workers have been on the job throughout the pandemic. What can they teach us about the safest way to lift a lockdown?
In places around the world, lockdowns are lifting to various degrees—often prematurely. Experts have identified a few indicators that must be met to begin opening nonessential businesses safely: rates of new cases should be low and falling for at least two weeks; hospitals should be able to treat all coronavirus patients in need; and there should be a capacity to test everyone with symptoms. But then what? What are the rules for reëntry? Is there any place that has figured out a way to open and have employees work safely, with each other and with their customers?
Well, yes: in health care. The Boston area has been a covid-19 hotspot. Yet the staff members of my hospital system here, Mass General Brigham, have been at work throughout the pandemic. We have seventy-five thousand employees—more people than in seventy-five per cent of U.S. counties. In April, two-thirds of us were working on site. Yet we’ve had few workplace transmissions. Not zero: we’ve been on a learning curve, to be sure, and we have no way to stop our health-care workers from getting infected in the community. But, in the face of enormous risks, American hospitals have learned how to avoid becoming sites of spread. When the time is right to lighten up on the lockdown and bring people back to work, there are wider lessons to be learned from places that never locked down in the first place.
These lessons point toward an approach that we might think of as a combination therapy—like a drug cocktail. Its elements are all familiar: hygiene measures, screening, distancing, and masks. Each has flaws. Skip one, and the treatment won’t work. But, when taken together, and taken seriously, they shut down the virus. We need to understand these elements properly—what their strengths and limitations are—if we’re going to make them work outside health care.
Start with hygiene. People have learned that cleaning your hands is essential to stopping the transfer of infectious droplets from surfaces to your nose, mouth, and eyes. But frequency makes a bigger difference than many realize. A study conducted at a military boot camp found that a top-down program of hand washing five times a day cut medical visits for respiratory infections by forty-five per cent. Research on the 2002 sars coronavirus outbreak found that washing hands more than ten times a day reduced people’s infection rate by even more. Disinfecting surfaces helps, too, and frequency probably matters, although I haven’t found good research on this. The key, it seems, is washing or sanitizing your hands every time you go into and out of a group environment, and every couple of hours while you’re in it, plus disinfecting high-touch surfaces at least daily.
That is not enough, however, because environmental transmission may account for as little as six per cent of covid-19 infections. sars-CoV-2, the virus that causes covid-19, spreads primarily through respiratory droplets emitted by infected people when they cough, sneeze, talk, or simply exhale; the droplets are then breathed in by others. (Loud talking has even been shown to generate measurably more droplets than quieter talking.) This is why physical distancing is so important. We have all now learned the six-foot rule for preventing transmission of contagion-containing droplets. In my hospital system, observers gently remind us to stand the prescribed distance apart on escalators and in the elevator line; we allow no more than four people on elevators that used to carry more than twenty (a nightmare at shift changes). We’ve turned as many internal meetings, patient visits, and team huddles as possible into video meetings, even if someone is right across the hall. When we can’t avoid face-to-face encounters, we’ve put up Plexiglas barriers and spaced our chairs and work stations farther apart.
The six-foot rule isn’t some kind of infectious-disease law, however. There’s no stop sign at six feet that respiratory droplets obey. Public-health guidelines, in fact, originally set the at-risk distance at three feet or less, based on theoretical models going back to the nineteen-thirties, simulation studies, and experience in previous outbreaks, such as a 1981 outbreak of infectious meningitis in a Texas elementary-school classroom. That outbreak began in a cluster of five girls seated together on one side of the room. One infected the other four. Investigators later took measurements: the distance from one girl’s seat to another was about two and a half feet. Close contact at lunchtime spread the Meningococcus bacteria to other children, who transmitted the disease in their classrooms. In all, thirty-one children became ill or were carriers, and the spread was mainly in two classrooms where the chair-to-chair distance was three feet or less.
Even then, it was already apparent that respiratory illnesses frequently travel farther. Past guidelines from the C.D.C. also cited a 1948 military study in which almost fifty young men with confirmed Streptococcus infection—strep throat—were asked to cough, sneeze (with the help of a sneezing powder), and talk. Petri dishes and air samplers were placed at various distances to capture bacteria. All three activities dispersed contagion. Sneezing was the worst.
In the most common pattern, bacteria grew only on petri dishes placed on the floor a foot and a half from the sneezer. In ten per cent of cases, bacteria were captured only by the air samplers. In twenty per cent, no streptococci were recovered anywhere. But one recruit spewed large quantities of bacteria into petri dishes and air samplers almost ten feet away. “This subject,” the report noted, “was really an unusually good atomizer.” They’d caught him at a time of particular infectivity. A few days later, he wasn’t nearly as infectious anymore.
It has now become well recognized that, under the right conditions of temperature, humidity, and air circulation, forceful coughing or sneezing can propel a cloudburst of respiratory droplets more than twenty feet. Yet it wasn’t until the sars epidemic in 2002, after several cases documenting more distant spread, that authorities doubled the at-risk distance from three to six feet. In one case, a man with sars on a three-hour flight from Hong Kong to Beijing infected twenty-two people, five of whom died. The twenty-three passengers in the same row or the three rows in front of the index patient bore the highest risk: eight fell ill. So did the flight attendant for the patient’s section. Extending the recommended distance made sense. But six feet was simply a choice guided by practicality. People seven rows away—around eighteen feet—developed sars, too.