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The World Health Organization (WHO) and the U.S. Centers for Disease Control and Prevention (CDC) have both revised their guidance on how SARS-CoV-2, the COVID-19 virus, is transmitted. Earlier, the two organizations said the virus was contained in droplets, which would fall harmlessly to the ground of their own weight within a few feet. Now, WHO and CDC are acknowledging that the virus is carried in tinier aerosols, which, as the WHO put it, “remain suspended in the air,” carrying pathogens around a room.
This revision repeats what the CDC stated in November in a softer version – but then quickly retracted as what a spokesperson called an “error of process.” According to a Washington Post report at the time, the CDC originally said it was “possible” that SARS-CoV-2 could be airborne, spreading through “small particles, such as those in aerosols.”
A Long and Frustrating Road for Aerosol Experts
The issue of airborne spread has been controversial for nearly a year. For example, a July article by Lidia Morawska of the Queensland University of Technology in Australia and Donald Milton of the University of Maryland School of Public Health, titled “It’s Time to Address Airborne Transmission of Coronavirus 2019,” drew the support of 237 scientists in an open letter. The authors wrote:
There is significant potential for inhalation exposure to viruses in microscopic respiratory drop- lets (microdroplets) at short to medium distances (up to several meters, or room scale), and we are advocating for the use of preventive measures to mitigate this route of airborne transmission.
Then in November, Kimberly Prather of the Scripps Institute of Oceanography, an expert on aerosols, and several colleagues wrote a letter to Science magazine, with an excellent description of how the virus is spread:
Viruses in droplets (larger than 100 µm) typically fall to the ground in seconds within 2 m of the source and can be sprayed like tiny cannonballs onto nearby individuals. Because of their limited travel range, physical distancing reduces exposure to these droplets. Viruses in aerosols (smaller than 100 µm) can remain suspended in the air for many seconds to hours, like smoke, and be inhaled….
Individuals with COVID-19, many of whom have no symptoms, release thousands of virus-laden aerosols and far fewer droplets when breathing and talking. Thus, one is far more likely to inhale aerosols than be sprayed by a droplet, and so the balance of attention must be shifted to protecting against airborne transmission.
As we reported in the first issue of this newsletter, a group of 13 U.S. public health experts, including such members of President Biden’s own COVID task force as Rick Bright, the former director of the Biomedical Advanced Research and Development Authority, and Michael Osterholm, a highly regarded epidemiologist at the University of Minnesota, called for “immediate action to strengthen measures to limit inhalation exposure to SARS-CoV-2.
The 13 scientists wrote in a letter Feb. 16 to Rochelle Walensky, director of the Centers for Disease Control and Prevention (CDC); Administration COVID Coordinator Jeff Zients; and Anthony Fauci, director of NIH’s National Institute of Allergy and Infectious Diseases:
For many months it has been clear that transmission through inhalation of small aerosol particles is an important and significant mode of SARS-CoV-2 virus transmission… Numerous studies have demonstrated that aerosols produced through breathing, talking, and singing are concentrated close to the infected person, can remain in air and viable for long periods of time and travel long distances within a room and sometimes farther.
Linsey Marr, an expert on aerosols at Virginia Tech who also signed the Science letter, was quoted as saying:
It’s time to stop pussyfooting around the fact that the virus is transmitted mostly through the air. If we properly acknowledge this, and get the right recommendations and guidance into place, this is our chance to end the pandemic in the next six months. If we don’t do this, it could very well drag on.
A Momentous Shift
In a long opinion piece on May 7 the New York Times, with the headline, “Why Did It Take So Long to Accept the Facts About COVID,” Zeynep Tufekci expressed the view that the updates by WHO and CDC were momentous. “A few sentences have shaken a century of science,” she wrote. “These latest shifts challenge key infection control assumptions,…putting a lot of what went wrong last year in context. They may also signal one of the most important advancements in public health during this pandemic.”
But she also pointed out that the two organizations gave the changes short shrift: “no news conference, no big announcement.” Perhaps they were embarrassed.
If the importance of aerosol transmission had been accepted early, we would have been told from the beginning that it was much safer outdoors, where these small particles disperse more easily, as long as you avoid close, prolonged contact with others. We would have tried to make sure indoor spaces were well ventilated, with air filtered as necessary.
Instead of blanket rules on gatherings, we would have targeted conditions that can produce superspreading events: people in poorly ventilated indoor spaces, especially if engaged over time in activities that increase aerosol production, like shouting and singing. We would have started using masks more quickly, and we would have paid more attention to their fit, too. And we would have been less obsessed with cleaning surfaces. Our mitigations would have been much more effective, sparing us a great deal of suffering and anxiety.
Super-Spreader Events 32.6x More Likely Indoors Than Outdoors
It is now crystal-clear that the COVID problem is indoors, and the way to mitigate SARS-CoV-2 spread is through smart measures to make the air inside not just clean but safe. In addition, what we are learning about COVID applies as well to other viruses, bacteria, and mold.
The data are now overwhelming. A systematic review by Tomasso Celeste Bulfone of the the University of California at Berkeley and colleagues in the Journal of Infectious Diseases looked at studies of peer-reviewed papers that compared interior and outdoor infection. Their conclusion: “Less than 10% of reported [SARS-CoV-2] transmissions occurred in outdoor settings [and] less than 5% of cases were related to outdoor occupations…. The odds of transmission or super-spreading are much lower outdoors.”
Bulfone and the other researchers noted that, of 318 identified outbreaks involving three or more cases in China reported to local Municipal Health Commissions in a one-month period, all occurred in indoor environments. And a Japanese study found that “the odds of a primary case transmitting COVID-19 in a closed environment were 18.7 times greater…compared to outdoor setting. The odds of a single case spreading to 3 or more individuals, which they defined as a super-spreader event, in closed environments compared to open air was 32.6 [to 1].” Another study of 10,926 cases found that less than one percent of transmissions occurred outdoors.
An April 13 opinion piece in the Denver Post headlined, “The CDC finally admits it was wrong about surface transmission of COVID-19,” Alex Huffman, an associate professor of chemistry at the University of Denver who studies biological aerosols, wrote:
Respiratory aerosols can be inhaled no matter where you are in a room. If you are standing within a few feet from someone infected, you breathe in a high concentration of virus and the risk is highest. Even if you are standing on the other side of the room, the virus can still infect you. At first, most public health agencies wrongly assumed that COVID-19 was spreading primarily through touch or droplets,…but increasingly deep and wide evidence has shown that inhalation of these smaller aerosols drives the majority of COVID spread.
None of this is new. It was merely ignored. Early in the pandemic, Canadian journalist Jonathan Kay analyzed 58 separate COVID-19 "super spreader" events in 28 countries. Kay's study was published in the blog Quillette on April 20, 2020. Kay is admits that he is not an epidemiologist and that his data are “substandard,” but they were also enormously powerful and impossible to overlook.
He found that 19 of the events “involved parties or liquor-fueled mass attendance festivals of one kind or another, including…celebrations of weddings, engagements and birthdays. Fourteen super-spreader events occurred at religious services or funerals and six involved “face-to-face business networking.” None concerned casual or incidental contact. Except for three incidents at sports events, where people were packed tight and spreading virus by cheering, all the events were outdoors. “It is notable, for instance,” Kay writes, “that the notorious outbreak at an Austrian ski resort is connected to a bartender and not, say, a lift operator.” Kay concludes his article with these prescient words:
If the principal modes of COVID-19 transmission can be narrowed down in this way, it would provide an enormous boon to the policymakers who are now starting to think about restarting our economies. Fighting this disease will always be hard. But it will be harder still if we fail to develop a proper understanding of the precise way it attacks us.
At last, it seems, the world is recognizing the nature of the beast.
Ventilation Is 'Unlikely to Succeed as the Prime Means of Protection'
The question is how best to prevent airborne SARS-CoV-2 from continuing to infect people, especially as they go back to school and work.
According to an extensive article in HPAC Engineering, the definitive answer is not ventilation – that is, the exchange of indoor for outdoor air through a heating and cooling, or HVAC, system.
Gary and Ken Elovitz of Energy Economics in Newton Centre, Mass., write:
The biggest danger for COVID-19 infection is close-range contact with infected people who are talking loudly or are otherwise exhaling heavily for at least several minutes. The HVAC system does not have much effect on those conditions.
The Elovitzes’ main contribution is to deploy the Wells-Riley equation, which uses “infectious particle concentration, exposure time, and outside air ventilation” to come up with a prediction of the “likelihood that a person will be infected by a virus.” (Academic research shows that, if anything, Wells-Riley underestimates risk.)
After the authors plug in the numbers, they conclude:
No practical amount of ventilation can be relied on or expected to protect occupants over long exposure times like the 6 or 8 hours people might spend together in an office or school classroom. Similarly, ventilation is unlikely to succeed as the prime means of protection for people in close contact in a small space like a private office. However, short term, intermittent contact in large spaces like a trip to the supermarket is unlikely to spread infection.
The authors say that “improved filtration can reduce the risk of transmission by reducing the concentration of infectious particles in the air.” But that reduction is by no means complete. They write that, on average, “MERV 13 filters might be 60% to 70% efficient at removing particles that contain viral material.” The authors also warn that higher-efficiency filters “have higher pressure drop,” which means reduced air flow and heating and cooling capacity. Bringing an HVAC system back up to its pre-filter levels of air flow requires an increased “motor load” – that is, a bigger-capacity system, which will use more energy and pose a greater threat to the environment.
Current Standards, Writes Allen of Harvard, Are Set for Bare Minimums
In fact, as an April 16 JAMA article by Joseph Allen of the Harvard T.H. Chan School of Public Health and Andrew Ibrahim of the University of Michigan points out, “an important flaw exists in how most buildings operate in that the current standards for ventilation and filtration in indoor spaces, except for hospitals are set for bare minimums and not designed for infection control.”
This is an indictment of the ventilation industry, which for decades has put people in jeopardy indoors. But the immediate point that Allen and Ibrahim are making is that HVAC systems generally do not produce enough air changes per hour for good health. In other words, these systems already require more power without loading them down with filtration systems.
But to get back to the Elovitzes…. They are also skeptical of ultraviolet disinfection systems because “ultraviolet radiation can harm people.” As for bipolar ionization systems, some of them “produce ozone as a byproduct,” and “there are no industry standards or test protocols” for these systems, “so performance is not verified.”
They conclude, “There is no solid evidence that HVAC systems can be a primary means of control” of COVID-19 spread.
COVID-19 Mitigation Can Damage the Environment
As Allen and Ibrahim write, “Increasing air exchange rates involves trade-offs including the added costs of moving more air as well as heating or cooling this volume of air.
Writing last year in the Wall Street Journal, Konrad Putzier amplified this point: “Some building owners find that they face a choice between lowering their energy use and keeping tenants safer from infection.” The truth is, devices do exist that destroy the virus with little or no effect on energy use – and those devices can be used with good effect as complements to ventilation. But simply increasing ventilation or adding filters to HVAC systems can both dramatically increase expenses and threaten the global climate.
The Journal article noted that in a study last year, “real-estate technology company Enertiv found that HVAC costs in office buildings increased 36% during the pandemic.” And buildings and construction account for 39% of all energy-related carbon emissions.
Ventilation is sometimes cited as a way to chase away pathogens or capture them if a filter is added. But the minimum standards (for example, five to six air changes per hour for schools) set by the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) are rarely met, as Allen and Ibrahim note. And some researchers believe the rates are too low to be effective.
Doubling the amount of outdoor air “reduces the chance of infection by up to 35% in densely packed venues such as restaurants,” writes Dyani Lewis in the journal Nature, referring to a preprint of a study by Liangzhu Wang and colleagues at Concordia University. But even wearing a mask indoors is “more effective than changing the air.”
Another scientist quoted in the Nature article points out that “the environmental cost of increased ventilation should give people pause.” Large HVAC companies have a stake in encouraging school administrators and building owners to increase the size and power of their systems – and thus, energy consumption -- to produce more air changes per hour.
It’s important to note that “air change” does not mean a 100% exchange of interior air with clean outdoor air. Instead, as the CDC calculates, it will still take 104 minutes in a room with four air changes per hour to eliminate at least 99.9% of contaminants – unless, of course, an infected person enters the room during those 104 minutes.
ASHRAE urged property managers in April to consider keeping HVAC systems running for 24 hours a day and bringing in more outside air. Because outside air typically has to be heated in the winter or cooled in the summer, it uses up more energy than merely recirculating indoor air. HVAC systems certainly have their place in the battle against COVID when combined with devices that inactivate the virus in the air, but running an HVAC system 24/7 seems deeply irresponsible environmentally.
Worse Than We Thought
COVID may be even worse than we thought. A Research Letter in JAMA on April 2 calculates that between March 2020, and Jan. 2, 2021, the U.S. experienced 22.9% more deaths than were expected before the pandemic. The study, by Seven H. Woolf of the Virginia Commonwealth University Medical School and colleagues, looked not just at COVID-19 deaths but at all-cause mortality. In fact, COVID represented only 72.4% of U.S. excess deaths for the nine-month period.
What were the other major causes? Heart disease, Alzheimer’s disease and other dementia, and diabetes. The authors found that these excess deaths showed surges that corresponded to COVID surges, pointing to COVID as the reason the other diseases took more lives than expected.
The researchers speculate that these deaths could actually have been caused by COVID but the infection was undocumented so mortality was attributed to another disease. Another possibility – which the authors cited in an earlier JAMA piece – is that the pandemic caused illnesses such as heart disease and diabetes to go untreated or undetected. In addition, fear of COVID-19 may have caused patients to neglect their care, unable or unwilling to visit physicians’ offices or go to emergency rooms.
The authors identify Mississippi, New Jersey, New York, Arizona, Alabama, Louisiana, South Dakota, North Dakota, New Mexico and Ohio as the states with the higher per capita rate of excess death. “New York,” they write, “experienced the largest relative increase in all-cause mortality” at 38.1%, a daunting figure.
Will We Ever Get Heard Immunity?
As nearly everyone knows, the CDC on April 27 issued new guidance for the 33% of Americans who are fully vaccinated against COVID-19. The big change is that if you’re vaccinated, you can “participate in outdoor activities and recreation without a mask, except in certain crowded settings and venues.” But right around the same time, vaccinations started to slow. As of May 3, the number of shots per day had dropped 50% when compared to just three weeks earlier.
More than 70% of Americans over 65 are vaccinated, and clearly the shots are having an effect. Overall, cases of COVID have dropped from a late January seven-day average of 260,000 to 45,000 last week, and deaths have declined from a seven-day average of 3,263 to 693.
It appears, nevertheless, that COVID-19 is not going to disappear because of herd immunity – that is, resistance to the spread of the disease because a high proportion of the population has had a previous infection or vaccination. A sobering report by Apoorva Mandavilli on May 5 surveyed experts, who now believe that the herd immunity threshold is not attainable — at least not in the foreseeable future, and perhaps not ever.”
Instead, Mandavilli writes:
The virus will most likely become a manageable threat that will continue to circulate in the United States for years to come, still causing hospitalizations and deaths but in much smaller numbers. How much smaller is uncertain and depends in part on how much of the nation, and the world, becomes vaccinated and how the coronavirus evolves.
The problem is that the virus is changing quickly into variants that spread too easily, and, at the same time, “vaccination is proceeding too slowly.” The main variant spreading in the U.S., called B.1.1.7 and first identified in Britain, is about 60% more transmissible than the virus that was first identified.
As Mandavilli writes in the New York Times:
Polls show that about 30 percent of the U.S. population is still reluctant to be vaccinated. That number is expected to improve but probably not enough. “It is theoretically possible that we could get to about 90 percent vaccination coverage, but not super likely, I would say,” said Marc Lipsitch, an epidemiologist at the Harvard T.H. Chan School of Public Health.
Variants are developing globally because only 8% of people worldwide have received a single dose, and those mutated viruses will inevitably move to the United States. An Axios headline on May 7 referred to “The race to avoid a possible ‘monster’ COVID variant.”
Reporter Eileen Drage O’Reilly quoted Josh Schiffer, an infectious disease expert at Fred Hutchinson Cancer Research Center, as saying, “If there is a new variant that's terrible — that ruins 2022 and brings us back to very dark times — it's almost a guarantee that it's percolating in an area of the world that's getting hit very hard now," Schiffer says.
All the more reason to get interior pathogen mitigation right.
COVID Solutions Bulletin
Our mission is to educate people on innovative solutions to the COVID-19 crisis in America. We need to get back to work, to school, to play – to enjoying life. We can’t get there without thwarting the current pandemic and preparing for the possibility of other pathogens to come.
COVID Solutions Bulletin is a publication providing regular updates on new and existing technologies that can help stop the spread of COVID-19, and help clear the air to open America back up.