surgical mask
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 reentry?
Healthcare workers at Mass General Brigham in the Boston area – a COVID-19 hotspot – have been at work throughout the pandemic. They have 75,000 employees. In April, two-thirds of them were working on site, yet they’ve had few workplace transmissions. Considering the circumstances, their numbers were exceptionally low, according to a Wall Street Journal article in May.
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, the article noted. Experts are looking at 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. These elements need to be properly understood – what their strengths and limitations are – and if people are going to make them work outside of the healthcare industry.
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 45%. Research on the 2002 sars coronavirus outbreak found that washing hands more than 10 times a day reduced people’s infection rate by even more.
Disinfecting surfaces is essential as well, but 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 frequently.
Unfortunately, that is still not enough. Environmental transmission may account for as little as 6% of covid-19 infections; 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 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. At Mass General Brigham, people are gently reminded to stand the prescribed distance apart on escalators and in the elevator line. No more than 4 people are allowed on elevators that used to carry more than 20. This may create a nightmare at shift changes but it’s essential. They have also turned as many internal meetings, patient visits, and team huddles as possible into video meetings, even if someone is right across the hall. When face-to-face encounters can be avoided, they have installed Plexiglas barriers and spaced chairs and workstations farther apart.
If 6 feet apart is good, father apart is even better. 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 20 feet.
Exposure time also matters. We may not know exactly how long is too long, but less than 15 minutes spent in the company of an infected person makes spread unlikely.
One of the most important ways to reduce the risk of spreading the virus has been daily screenings of all employees, patients, and visitors for symptoms of covid-19 at Mass General Brigham. Any time a doctor wants to enter a hospital building, they have to go to a website, log in with an employee identification, and confirm they have not developed a single sign of the disease – a new fever, cough, sore throat, shortness of breath, loss of taste or smell, or even just nasal congestion or a runny nose. Administrators have also considered adding a formal temperature check with an infrared touchless thermometer. Although 90% of symptomatic covid-19 patients eventually develop fevers, early on, fever is present less than half the time. So, it’s actually the mild symptoms that are most important to screen for.
Testing when people have symptoms is important; with a positive result, a case can be quickly identified, and close contacts at work and at home can be notified. And, with a negative result, people can quickly get back to work. Due to the proliferation of false-negative test results, people should probably still be required to wait until any fever has been resolved, and symptoms have improved, for 72 hours.
Self-screening, obviously, is far from foolproof. Anyone could lie. Nonetheless, in the first week of rollout, more than 500 people at Mass General Brigham indicated through the website that they had symptoms. Through the first week of May, symptoms, often mild, prompted more than 11,000 staff members to stay home and receive testing. Fourteen hundred tested positive for the coronavirus and avoided infecting patients and colleagues.
Daily check-ins are equally important for less measurable reasons: they send the right message. Calling in sick as not a sign of weakness; toughing it out is now a shameful act of disloyalty.
Even the most scrupulous check-ins, however, can do only so much in this pandemic, because the virus can make people infectious before they develop symptoms of illness. Studies now consistently indicate that infectivity starts before symptoms do, that it peaks right around the day that they start, and that it declines substantially by five days or so – a pattern similar to that of influenza.
That’s why masks are also an important tool. They provide “source control” – blocking the spread of respiratory droplets from a person with active, but perhaps unrecognized, infection.
So how effective are surgical masks? A study published in Nature in April shows that, if worn properly and with the right fit, surgical masks are effective at blocking 99% of the respiratory droplets expelled by people with coronaviruses or influenza viruses. The material of a double-layered cotton mask – the kind many people have been making at home – can block droplet emissions, as well. The virus does not last long on cloth; viral counts drop 99% in three hours. Cloth masks aren’t as breathable as surgical masks, though, which is obviously important.
Cloth masks feel warm and smothering in comparison to surgical masks, and people tend to loosen them, wear them below their noses, or take them off more frequently. The fit of improvised masks is also more variable and typically much worse. A comparison study found that surgical masks did three times better than homemade masks at blocking outward transmission of respiratory viruses.
That doesn’t mean you should ditch your T-shirt mask. A recent, extensive review of the research from an international consortium of scientists suggests that if at least 60% of the population wore masks that were just 60% effective in blocking viral transmission – which a well-fitting, two-layer cotton mask is – the epidemic could be stopped. The more effective the mask, the bigger the impact.
There are masks specifically designed to not only protect others but also protect the wearer from infection: N95 respirators. These are masks that are designed to fit tightly around the nose and mouth, so that the air you breathe comes entirely through the mask, not around it. They use a filter material with a higher electrostatic charge that blocks at least 95% of airborne particles as small as 0.3 microns. If we had an unlimited supply of N95s, all health-care workers would wear them – indeed, lots of people would. But supplies are scarce, even in hospitals.
Even N95s aren’t foolproof. The seal around the face is often imperfect. Your eyes remain a portal of entry for the virus. And breathing through an N95 all day is uncomfortable. Talking and being heard while wearing one is also a challenge. So, people usually prefer to use them for limited periods of time. Just beware of N95 masks with a valve. The valve makes exhalation easier by getting rid of outward filtration. In other words: I protect me; I expose you. These masks are designed for people working in industrial settings where the protection is against dust or asbestos, not viruses. Some cities have, rightly, banned the use of those masks during the pandemic.
Evidence of the benefits of mandatory masks is now overwhelming. The question is whether supplies will keep up with demand. Factories are increasing production of both surgical masks and N95s as rapidly as possible, but they don’t come close to meeting health-care workers’ needs, let alone supplying the general public, and they won’t for months to come.
In order to stretch their supplies, Mass General Brigham currently limits workers to just a mask a day. They’ve also found ways to decontaminate masks for reuse, which hasn’t been easy. If a disinfectant gets a mask wet, the electrostatic charge is lost. A major breakthrough was the development of a hydrogen-peroxide decontamination system by Battelle, a nonprofit research institute in Columbus, Ohio. Battelle’s machine creates hydrogen-peroxide vapor that, testing shows, maintains mask filtration, potentially for up to 20 cycles.
Domestic production of masks in the U.S. has been delayed by inadequate federal support and coordination, but it is nonetheless ramping up.
The four pillars of a safety strategy – hygiene, distancing, screening and masks – may not return us to normal life, but, when signs indicate that the virus is under control, they could get people out of their homes and moving again.
Culture is the fifth, and arguably the most difficult, pillar of a new combination therapy to stop the coronavirus. People tend to focus on two desires: safety and freedom; keep me safe and leave me alone. People need to embrace the desire to keep others safe, not just themselves.
There is still much more to learn, such as whether people can safely work at less than six feet apart if everyone has masks on, and for how long. But answers will only come through commitment to abiding by new norms and measuring results, not through wishful thinking.
As political leaders push to reopen businesses and schools, they are beginning to talk about the tools that have kept health-care workers safe. The science says that these tools can work. But it’s worrying how little officials are discussing what it takes to deliver them as a whole package and monitor their effectiveness.
Source: The New Yorker
