McIlvaine Coronavirus Market Ale

Michael Mina of Harvard says it is important to distinguish medical from public health guidance. This is good advice. In fact it is important to also distinguish guidance for vaccine manufacture.

It is also desirable to distinguish between sub segments. The guidance for personnel entering an isolation unit are far different than for a person at the registration desk in a hospital.

Application	Filtration Efficiency %
Medical
Registration	90
Non infectious	95
Infectious	99.99
Pharmacy	99.99
Vaccine Mfg.
Fill and finish	99.999
Adjacencies	99.9
Public High Positivity Zone
Open Parks	60
City Streets	90
Elevators	95
Subways	99

The efficiency needs can be achieved with a combination of filters and masks. If there are filter cubes on the city streets at intersections the need for more efficient masks is less. If the elevator has a HEPA filter and laminar air flow there is less of a burden on the mask. This combination of filters can be conceived as the swiss cheese defense program as explained below.

This concept was the basis of an article by Siobhan Roberts published Dec. 5, 2020 in the NY Times.

Lately, in the ongoing conversation about how to defeat the coronavirus, experts have made reference to the “Swiss cheese model” of pandemic defense.

The metaphor is easy enough to grasp: Multiple layers of protection, imagined as cheese slices, block the spread of the new coronavirus, SARS-CoV-2, the virus that causes Covid-19. No one layer is perfect; each has holes, and when the holes align, the risk of infection increases. But several layers combined — social distancing, plus masks, plus hand-washing, plus testing and tracing, plus ventilation, plus government messaging — significantly reduce the overall risk. Vaccination will add one more protective layer.

“Pretty soon you’ve created an impenetrable barrier, and you really can quench the transmission of the virus,” said Dr. Julie Gerberding, executive vice president and chief patient officer at Merck, who recently referenced the Swiss cheese model when speaking at a virtual gala fund-raiser for MoMath, the National Museum of Mathematics in Manhattan.

“But it requires all of those things, not just one of those things,” she added. “I think that’s what our population is having trouble getting their head around. We want to believe that there is going to come this magic day when suddenly 300 million doses of vaccine will be available and we can go back to work and things will return to normal. That is absolutely not going to happen fast.”

Rather, Dr. Gerberding said in a follow-up email, expect to see “a gradual improvement in protection, first among the highest need groups, and then more gradually among the rest of us.” Until vaccines are widely available and taken, she said, “we will need to continue masks and other common-sense measures to protect ourselves and others.”

In October, Bill Hanage, an epidemiologist at the Harvard T.H. Chan School of Public Health, retweeted an infographic rendering of the Swiss cheese model, noting that it included “things that are personal *and* collective responsibility — note the ‘misinformation mouse’ busy eating new holes for the virus to pass through.”

“One of the first principles of pandemic response is, or ought to be, clear and consistent messaging from trusted sources,” Dr. Hanage said in an email. “Unfortunately the independence of established authorities like the C.D.C. has been called into question, and trust needs to be rebuilt as a matter of urgency.” A catchy infographic is a powerful message, he said, but ultimately requires higher-level support.

The Swiss cheese concept originated with James T. Reason, a cognitive psychologist, now a professor emeritus at the University of Manchester, England, in his 1990 book, “Human Error.” A succession of disasters including the Challenger shuttle explosion, Bhopal and Chernobyl — motivated the concept, and it became known as the “Swiss cheese model of accidents,” with the holes in the cheese slices representing errors that accumulate and lead to adverse events.

The model has been widely used by safety analysts in various industries, including medicine and aviation, for many years. (Dr. Reason did not devise the “Swiss cheese” label; that is attributed to Rob Lee, an Australian air-safety expert, in the 1990s.) The model became famous, but it was not accepted uncritically; Dr. Reason himself noted that it had limitations and was intended as a generic tool or guide. In 2004, at a workshop addressing an aviation accident two years earlier near Überlingen, Germany, he delivered a talk with the title, “Überlingen: Is Swiss cheese past its sell-by date?”

In 2006, a review of the model, published by the Eurocontrol Experimental Center, recounted that Dr. Reason, while writing the book chapter “Latent errors and system disasters,” in which an early version of the model appears, was guided by two notions: “the biological or medical metaphor of pathogens, and the central role played by defenses, barriers, controls and safeguards (analogous to the body’s autoimmune system).”

The cheese metaphor now pairs fairly well with the coronavirus pandemic. Ian M. Mackay, a virologist at the University of Queensland, in Brisbane, Australia, saw a smaller version on Twitter, but thought that it could do with more slices, more information. He created, with collaborators, the “Swiss Cheese Respiratory Pandemic Defense” and engaged his Twitter community, asking for feedback and putting the visualization through many iterations. “Community engagement is very high!” he said. Now circulating widely, the infographic has been translated into more than two dozen languages.

“This multilayered approach to reducing risk is used in many industries, especially those where failure could be catastrophic,” Dr. Mackay said, via email. “Death is catastrophic to families, and for loved ones, so I thought Professor Reason’s approach fit in very well during the circulation of a brand-new, occasionally hidden, sometimes severe and occasionally deadly respiratory virus.”

The following is an edited version of a recent email conversation with Dr. Mackay by the Washington Post.

A. The real power of this infographic — and James Reason’s approach to account for human fallibility — is that it’s not really about any single layer of protection or the order of them, but about the additive success of using multiple layers, or cheese slices. Each slice has holes or failings, and those holes can change in number and size and location, depending on how we behave in response to each intervention.

Take masks as one example of a layer. Any mask will reduce the risk that you will unknowingly infect those around you, or that you will inhale enough virus to become infected. But it will be less effective at protecting you and others if it doesn’t fit well, if you wear it below your nose, if it’s only a single piece of cloth, if the cloth is a loose weave, if it has an unfiltered valve, if you don’t dispose of it properly, if you don’t wash it, or if you don’t sanitize your hands after you touch it. Each of these are examples of a hole. And that’s in just one layer.

To be as safe as possible, and to keep those around you safe, it’s important to use more slices to prevent those volatile holes from aligning and letting virus through.

A. Distance is the most effective intervention; the virus doesn’t have legs, so if you are physically distant from people, you avoid direct contact and droplets. Then you have to consider inside spaces, which are especially in play during winter or in hotter countries during summer: the bus, the gym, the office, the bar or the restaurant. That’s because we know SARS-CoV-2 can remain infectious in aerosols (small floaty droplets) and we know that aerosol spread explains Covid-19 superspreading events. Try not to be in those spaces with others, but if you have to be, minimize your time there (work from home if you can) and wear a mask. Don’t go grocery shopping as often. Hold off on going out, parties, gatherings. You can do these things later.

A. The misinformation mouse can erode any of those layers. People who are uncertain about an intervention may be swayed by a loud and confident-sounding voice proclaiming that a particular layer is ineffective. Usually, that voice is not an expert on the subject at all. When you look to the experts — usually to your local public health authorities or the World Health Organization — you’ll find reliable information.

An effect doesn’t have to be perfect to reduce your risk and the risk to those around you. We need to remember that we’re all part of a society, and if we each do our part, we can keep each other safer, which pays off for us as well.

Another example: We look both ways for oncoming traffic before crossing a road. This reduces our risk of being hit by a car but doesn’t reduce it to zero. A speeding car could still come out of nowhere. But if we also cross with the lights, and keep looking as we walk, and don’t stare at our phone, we drastically reduce our risk of being hit.

We’re already used to doing that. When we listen to the loud nonexperts who have no experience in protecting our health and safety, we are inviting them to have an impact in our lives. That’s not a risk we should take. We just need to get used to these new risk-reduction steps for today’s new risk — a respiratory virus pandemic, instead of a car.

A. We each need to do our part: stay apart from others, wear a mask when we can’t, think about our surroundings, for example. But we can also expect our leadership to be working to create the circumstances for us to be safe — like regulations about the air exchange inside public spaces, creating quarantine and isolation premises, communicating specifically with us (not just at us), limiting border travel, pushing us to keep getting our health checks, and providing mental health or financial support for those who suffer or can’t get paid while in a lockdown.

A. We each use these approaches in everyday life. But for the pandemic, this all feels new and like a lot of extra work. Because everything is new. In the end, though, we’re just forming new habits. Like navigating our latest phone’s operating system or learning how to play that new console game I got for my birthday. It might take some time to get across it all, but it’s worthwhile. In working together to reduce the risk of infection, we can save lives and improve health.

And as a bonus, the multilayered risk reduction approach can even decrease the number of times we get the flu or a bad chest cold. Also, sometimes slices sit under a mandate — it’s important we also abide by those rules and do what the experts think we should. They’re looking out for our health.

Elaine Glusac covered the activities in this travel segment in an article in the NY Times published Dec. 3, 2020. Her article shows that while HEPA filters and other reliable air cleaning devices are being used there is very likely false optimism about other technologies.

When the coronavirus first hit, hotels quickly adopted enhanced cleaning polices, including germ-killing electrostatic spraying and ultraviolet light exposure in guest rooms and public areas.

But as research on virus spread has shifted focus from surface contact to airborne transmission, some hotels and cruise ships are scrubbing the very air travelers breathe with a variety of air filtration and treatment systems.

“The best amenity that any hotel could provide under those circumstances is safety, especially in the air,” said Carlos Sarmiento, the general manager of the Hotel Paso del Norte in El Paso, Texas. The 1912 vintage hotel recently reopened after a four-year renovation that included installing a new air purification system called Plasma Air that emits charged ions intended to neutralize the virus and make particles easier to filter out.

With the new air-scrubbing campaigns, hotels are following airlines, many of which have hospital-grade, high-efficiency particulate air (HEPA) filters that are said to be over 99 percent effective in capturing tiny virus particles, including the coronavirus.

Hotels and cruise ships can more easily ensure social distancing than airplanes, but, given the recent research on the importance of enhanced air filtration, some are adding air-cleaning dimensions to their heating, ventilation and air conditioning (HVAC) systems, which already aim to remove dust, smoke, odors and allergens.

Researchers, including those at New Orleans’s Tulane University, have found that the tiny aerosol particles of SARS-CoV-2 that are emitted when someone with the virus speaks or breathes can remain in the air for up to 16 hours.

Along with social distancing, mask wearing is the first line of defense against breathing contaminated air indoors, said Dr. Philip M. Tierno Jr., a professor of microbiology and pathology at New York University School of Medicine, who has consulted with HVAC companies.

“HVAC systems are of great significance in reducing the amount of airborne particles since this virus can be spread in an airborne fashion,” he added, calling the tiniest aerosols “the most dangerous.”

Air cleaning technologies include bipolar ionization systems, which, according to their manufacturers, send charged ions out on air currents that damage the surface of the virus and inactivate it. They may also bind with the virus aerosols, causing them to fall or be more easily filtered out.

However, some experts are skeptical, pointing to evidence that these systems may introduce ozone or particles that are dangerous if inhaled. ASHRAE, a professional society of air-conditioning, heating and refrigerating engineers, notes that the technology is still “emerging” and lacks “scientifically-rigorous, peer-reviewed studies.” The bipolar ionization company AtmosAir Solutions provided results of tests performed by the independent Microchem Laboratory, which evaluates sanitizing products, that found the technology reduced the presence of coronavirus by more than 99 percent within 30 minutes of exposure.

“We talk about it as nature’s cleaning device,” said Kevin Devlin, the chief executive of WellAir, which sells the bipolar ionization system Plasma Air installed at the Hotel Paso del Norte. He noted that air at high elevations in the mountains that “smells clean” has higher amounts of ions.

Some anti-viral HVAC systems feature germicidal ultraviolet light in the ductwork (the Food and Drug Administration states that ultraviolet-C lamps have been shown to inactivate the virus). Such a system was installed at The Distillery Inn in Carbondale, Colo., and includes a three-hour disinfection cycle between guests.

Systems often use a combination of these technologies with efficient air filters that remove contaminants. Filters with Minimum Efficiency Reporting Values (MERV) of 13 or higher are best at capturing the coronavirus, according to the Environmental Protection Agency.

According to its website, the agency “recommends increasing ventilation with outdoor air and air filtration as important components of a larger strategy that includes social distancing, wearing cloth face coverings or masks, surface cleaning and disinfecting, handwashing, and other precautions.”

“In a transient environment, like a hotel, motel or dormitory, you don’t know who was there before you and what their health was,” said Wes Davis, the director of technical services with the Air Conditioning Contractors of America, a trade association, adding that good housekeeping is a top priority in such places. “As for the other items like ultraviolet exposure or ionization, every little bit helps, but I’m not quite sure any of them is the perfect solution. It’s more like a concert.”

Throughout the summer, the Madison Beach Hotel, part of Hilton’s Curio Collection of hotels, in Madison, Conn., used its outdoor spaces for dining and even holding meetings in tents. But with the approach of cold weather, HVAC contractors installed an air purification system that uses UV light and ionized hydrogen peroxide in most public areas of the hotel, including the indoor restaurant and meeting rooms. Spa treatment rooms each have their own portable air purification systems.

“We wanted to create an environment that was as safe as possible,” said John Mathers, the hotel’s general manager, adding that each guest room has its own closed HVAC system that doesn’t mingle with others and thus doesn't require extra purifying. “The air being recirculated in your room is your air.”

But many hotels are bringing units into the guest rooms for extra assurance. In Rhode Island, rooms at the Weekapaug Inn and Ocean House hotel, both run by Ocean House Management, have Molekule air purifiers that destroy pollutants and viruses at a rate above 99 percent, according to the independent testing group Aerosol Research and Engineering Laboratories.

Larger units were recently added to restaurants and public spaces, and the portable units have become a top seller, starting at around $500, in Ocean House’s gift shop.

Decisions about installing air purification systems tend to happen at the property or ownership level, rather than the brand level. But Hilton has AtmosAir’s bipolar ionization air purification systems in its Five Feet to Fitness rooms, more than 100 guest rooms across 35 hotels that double as mini gyms with weights, indoor cycles and meditation chairs.

Many hotels have long offered allergy-free or wellness rooms to travelers that feature heightened purification systems. Pure Wellness has its Pure Room technology that claims to eliminate viruses, bacteria and fungi, including air filters effective enough to trap the coronavirus, in over 10,000 rooms worldwide.

The 112-passenger SeaDream I from the SeaDream Yacht Club took many precautions — including pre-embarkation Covid-19 testing, electrostatic fogging of public areas and UV light sterilization after nightly turndown — before it launched its winter season from Barbados on Nov. 7, and still a passenger got the virus within days of departure, cutting the trip short. Eventually nine infections were diagnosed and the line canceled future 2020 sailings. (The cruise line did not respond to a requests for comment on whether any improvement had been made to the ship’s ventilation system.)

SeaDream’s failed cruise exemplifies the challenges the entire industry faces. Some health experts think that upgraded air filtration could help. Adopting systems that are “aimed at reducing occupant exposure to infectious droplets/aerosols,” and upgrading HVAC systems with MERV 13 filters were among 74 critical recommendations to ship lines made by the Healthy Sail Panel, a group of public health experts assembled by Royal Caribbean Group and Norwegian Cruise Line Holdings in September.

The Centers for Disease Control and Prevention maintains that ships remain vulnerable to spreading infection based on population density and the inability of crew in particular to maintain social distance in their work spaces and living quarters. Still, cruising is expected to resume in U.S. waters for ships carrying 250 or more passengers and crew in the first half of 2021, pending certification under the C.D.C.’s Framework for Conditional Sailing Order, which spells out minimum standards for social distancing, face coverings and hand hygiene, but does not mention air circulation systems.

Despite the C.D.C.’s lack of emphasis on air filtration, some cruise companies are upgrading their ventilation systems, in addition to designating quarantine areas and reconfiguring dining rooms.

Norwegian Cruise Line, for example, has announced its ships will use HEPA filters. And Princess Cruises has said it will upgrade its ships’ HVAC systems to MERV 13 filters, refresh the air in cabins and public spaces every five to six minutes, and install HEPA filters in areas such as medical centers and isolation rooms.

The new Virgin Voyages cruise line, whose launch has been delayed by the pandemic, confirmed it had installed AtmosAir bipolar ionization systems on its inaugural ship, the roughly 2,700-passenger Scarlet Lady, and a second ship coming in 2021.

“This was a multimillion-dollar investment and based on our research and growing understanding of the virus, was an important step to sailing safely,” wrote Tom McAlpin, the chief executive of Virgin Voyages, in an email.