As the holidays approached, two professors have developed a tool to asses the risk of contracting COVID-19 in various indoor settings and made it available for the public at large.
Titled the COVID-19 Indoor Safety Guideline, the interactive website, developed by Massachusetts Institute of Technology professors Martin Bazant and John Bush, provides calculations which estimate how many people can remain within an enclosed space, and for how long, before they are theoretically exposed to the virus.
Martin Bazant and John Bush, both professors at the Massachusetts Institute of Technology with backgrounds in fluid mechanics and mathematics, are endeavoring to advance mitigation guidance with a data-driven risk assessment approach.
In coordination with Kasim Khan, an energy consulting associate and recent college graduate, Bazant and Bush developed the digital simulation and included several factors, such as room size, ventilation, mask use and the number of people present, to help users determine the level of risk.
Users can specify values for each of these variables themselves, and the module generates risk assessments accordingly. It gives users an estimated period of time, in either hours or days, that differently sized groups of people could theoretically interact before contracting the virus, assuming one person is already infected.
“The safety guideline is simple enough to reveal trends and enable useful calculations, while maintaining quantitative relevance,” Bazant told Newsweek, noting that it helps to illuminate “the relative importance of using facemasks, good ventilation, low occupant density, soft speech, light activity, air filtration, and moderately high humidity, roughly in that order, as strategies to mitigate transmission.”
The app is gaining public attention as coronavirus transmission runs rampant across the U.S. In December, the country is diagnosing cases, admitting hospital patients and recording fatalities at daunting rates. The onset of colder temperatures poses new threats for further proliferation of COVID-19. People are congregating indoors, where risks of contracting the virus are higher, especially during a season that, experts say, lends itself to elevated transmission on its own.
Public health authorities offer a number of mitigation tactics aimed at reducing the spread of COVID-19, championing face masks and six feet of physical distance as some of the most effective measures. And one health experts told Newsweek that while the digital tool can serve as a guide for individuals during the pandemic, users should not consider the results obtained as absolute.
The risk assessment app does not account for situations in which none of the individuals present are wearing face masks. In an FAQ section that appears beside the simulation itself, creators point to “an additional risk of short-range transmission” of COVID-19 when neither masks nor face shields are worn. They estimate this additional risk in a scientific paper that is also published, but currently undergoing peer reviews.
Bazant and Bush determined the module’s parameters after analyzing a handful of super-spreader events that took place across the world during the earlier part of the pandemic. It is fundamentally rooted in the idea that COVID-19 predominantly spreads through airborne transmission, a conclusion that Bazant told Newsweek became evident during the research process.
The consistency of their results, Bazant said, “provides strong support to the already overwhelming evidence for airborne transmission as the dominant mechanism for spreading [COVID-19],” he said.
“John [Bush}’s work on the fluid mechanics of coughing and sneezing made clear that pathogens borne on exhaled aerosol droplets could extend much farther than six feet,” Bazant explained. The professor added that his experience in chemical engineering suggested that “air flow characteristics, room occupancy and exposure time could be more important variables controlling transmission than physical distance.”
Information about primary modes of COVID-19 transmission, and which are most prevalent, have developed over the course of the pandemic. The Centers for Disease Control and Prevention (CDC) originally maintained that transmission occurred as a result of close contact with an infected person, when respiratory particles carrying the virus were most likely to reach others through coughs, sneezes or general breathing. Direct contact with an infected person through a hug or handshake, and sometimes through contact with a contaminated surface, were also quickly recognized as forms of transmission.
This early understanding of how the virus can spread informed the CDC’s initial mitigation guidelines. Issued shortly after the U.S. outbreak began, its recommendations suggested that everyone wear face masks in public spaces, remain six feet apart from those outside of their immediate households and wash their hands frequently to lower transmission risks.
Although the CDC still upholds that COVID-19 spreads most often in close contact scenarios, it released additional guidance in the fall acknowledging the potential for airborne COVID-19 transmission as well.
“It is possible that COVID-19 may spread through droplets and airborne particles that are formed when a person who has COVID-19 coughs, sneezes, sings, talks or breathes,” reads a notice shared to one of the CDC’s virus resource pages in December. “There is growing evidence that droplets and airborne particles can remain suspended in the air and be breathed in by others, and travel distances beyond 6 feet (for example, during choir practice, in restaurants, or in fitness classes).”
The ongoing debate about the pervasiveness of airborne COVID-19 transmission has persisted throughout the year. While some scientists, like Bazant and Bush, believe it to be a dominant source of the virus’ spread, others say outbreak patterns indicate this mode is relatively uncommon. The CDC bases its recommendations on the latter view. It notes that epidemiologists would expect a primarily airborne virus to infect a population more rapidly and aggressively than COVID-19 has in the U.S. since March.
Dr. Amesh Adalja, a senior scholar at the Johns Hopkins Center for Health Security whose work centers on infectious diseases, pandemic preparedness and biosecurity, regarded the COVID-19 Indoor Safety Guideline’s foundational hypotheses about transmission as its most significant limitation. He did, however, note the present lack of “risk calculating” tools available to the general public.
“I do think that this type of thing makes sense to do in general,” Adalja told Newsweek of the risk assessment app, saying models like these can act as important resources for people to gauge transmission risks in a more concrete way. “There’s definitely a need for people to have some idea of what the relative safety of certain activities are, and then they can make much more informed decisions.”
“I would just say this is about airborne transmission, and it may be something that is not necessarily applicable to everyday situations because it’s very focused on airborne,” he continued. “And I think that’s just something to keep in mind when you’re looking at it.”
Newsweek reached out to the CDC for comment but did not receive a reply in time for publication.