Masks, ventilation stop COVID spread better than social distancing, study shows

 A new study from the University of Central Florida suggests that masks and a good ventilation system are more important than social distancing for reducing the airborne spread of COVID-19 in classrooms.

The research, published recently in the journal Physics of Fluids, comes at a critical time when schools and universities are considering returning to more in-person classes in the fall.

"The research is important as it provides guidance on how we are understanding safety in indoor environments," says Michael Kinzel, an assistant professor in UCF's Department of Mechanical and Aerospace Engineering and study co-author.

"The study finds that aerosol transmission routes do not display a need for six feet social distancing when masks are mandated," he says. "These results highlight that with masks, transmission probability does not decrease with increased physical distancing, which emphasizes how mask mandates may be key to increasing capacity in schools and other places."

In the study, the researchers created a computer model of a classroom with students and a teacher, then modeled airflow and disease transmission, and calculated airborne-driven transmission risk.

The classroom model was 709 square feet with 9-foot-tall ceilings, similar to a smaller-size, university classroom, Kinzel says. The model had masked students -- any one of whom could be infected -- and a masked teacher at the front of the classroom.

The researchers examined the classroom using two scenarios -- a ventilated classroom and an unventilated one -- and using two models, Wells-Riley and Computational Fluid Dynamics. Wells-Riley is commonly used to assess indoor transmission probability and Computational Fluid Dynamics is often used to understand the aerodynamics of cars, aircraft and the underwater movement of submarines.

Masks were shown to be beneficial by preventing direct exposure of aerosols, as the masks provide a weak puff of warm air that causes aerosols to move vertically, thus preventing them from reaching adjacent students, Kinzel says.

Additionally, a ventilation system in combination with a good air filter reduced the infection risk by 40 to 50% compared to a classroom with no ventilation. This is because the ventilation system creates a steady current of air flow that circulates many of the aerosols into a filter that removes a portion of the aerosols compared to the no-ventilation scenario where the aerosols congregate above the people in the room.

These results corroborate recent guidelines from the U.S. Centers for Disease Control and Prevention that recommend reducing social distancing in elementary schools from six to three feet when mask use is universal, Kinzel says.

"If we compare infection probabilities when wearing masks, three feet of social distancing did not indicate an increase in infection probability with respect to six feet, which may provide evidence for schools and other businesses to safely operate through the rest of the pandemic," Kinzel says.

"The results suggest exactly what the CDC is doing, that ventilation systems and mask usage are most important for preventing transmission and that social distancing would be the first thing to relax," the researcher says.

When comparing the two models, the researchers found that Wells-Riley and Computational Fluid Dynamics generated similar results, especially in the non-ventilated scenario, but that Wells-Riley underpredicted infection probability by about 29 percent in the ventilated scenario.

As a result, they recommend some of the additional complex effects captured in Computational Fluid Dynamics be applied to Wells-Riley to develop a more complete understanding of risk of infection in a space, says Aaron Foster, a doctoral student in UCF's Department of Mechanical and Aerospace Engineering and the study's lead author.

"While the detailed Computational Fluid Dynamics results provided new insights into the risk variation and distance relationships, they also validated the more commonly used Wells-Riley models as capturing the majority of the benefit of ventilation with reasonable accuracy," Foster says. "This is important since these are publicly available tools that anyone can use to reduce risk."

The research is part of a larger overall effort to control airborne disease transmission and better understand factors related to being a super-spreader. The researchers are also testing the effects of masks on aerosol and droplet transmission distance. The work is funded in part by the National Science Foundation.

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Study shows meaningful lockdown activity is more satisfying than busyness

 New research shows people who pursue meaningful activities -- things they enjoy doing -- during lockdown feel more satisfied than those who simply keep themselves busy.

The study, published in PLOS ONE, shows you're better off doing what you love and adapting it to suit social distancing, like swapping your regular morning walk with friends for a zoom exercise session.

Simply increasing your level of activity by doing mindless busywork will leave you unsettled and unsatisfied.

Co-lead researcher Dr Lauren Saling from RMIT University in Melbourne, Australia said while novelty lockdown activities -- like baking or painting -- have their place, trying to continue what you enjoyed before lockdown can be more rewarding.

"Busyness might be distracting but it won't necessarily be fulfilling," she said.

"Rather, think about what activities you miss most and try and find a way of doing them."

Survey participants rated their level of wellbeing as it was during social distancing and retrospectively one month beforehand.

They also indicated how much time they spent engaged in various activities and nominated how important each activity was for them.

Although participants reported feeling more positive emotions while doing novelty 'meaningless' activities like binge watching TV, they also felt more negative emotions -- they felt unhappy just as much as they felt happy.

But when substituting activities enjoyed before lockdown -- like dining with friends -- for a virtual alternative, their positive and negative emotions were more subdued.

Saling said busyness riles you up, prompting you to change your behaviour, but meaningful activity -- doing what you enjoy -- calms you down.

"Extreme emotions are not necessarily a good thing," she said.

"Emotions are a mechanism to make you change your behaviour.

"But when you're doing what you love, it makes sense that you feel more balanced -- simply keeping busy isn't satisfying."

Saling said the study challenged assumptions that we are either happy or sad and that we can stave off sadness by keeping busy.

Rather, those who kept busy with mindless tasks felt more frustrated and even when they were happy felt less fulfilled.

"The study showed positive and negative affect worked together, not as opposites," Saling said.

"Respondents who simply stayed busy during lockdown reported an increase in both positive and negative emotions.

"This heightened emotionality will tend to shift you away from activity in general and towards meaningful activity."

The study also found the biggest change in positive emotions before and during lockdown was experienced by people aged under 40.

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Large, delayed outbreaks of endemic diseases possible following COVID-19 controls

 

Illustration, people wearing masks.

Measures to reduce the spread of COVID-19 through non-pharmaceutical interventions (NPIs) such as mask wearing and social distancing are a key tool in combatting the impact of the ongoing coronavirus pandemic. These actions also have greatly reduced incidence of many other diseases, including influenza and respiratory syncytial virus (RSV).

Current reductions in these common respiratory infections, however, may merely postpone the incidence of future outbreaks, according to a study by Princeton University researchers published Nov. 9 in the Proceedings of the National Academy of Sciences.

"Declines in case numbers of several respiratory pathogens have been observed recently in many global locations," said first author Rachel Baker, an associate research scholar at the High Meadows Environmental Institute (HMEI) at Princeton University.

"While this reduction in cases could be interpreted as a positive side effect of COVID-19 prevention, the reality is much more complex," Baker said. "Our results suggest that susceptibility to these other diseases, such as RSV and flu, could increase while NPIs are in place, resulting in large outbreaks when they begin circulating again."

Baker and her co-authors found that NPIs could lead to a future uptick in RSV -- an endemic viral infection in the United States and a leading cause of lower respiratory-tract infections in young infants -- but that the same effect was not as pronounced for influenza.

"Although the detailed trajectory of both RSV and influenza in the coming years will be complex, there are clear and overarching trends that emerge when one focuses on some essential effects of NPIs and seasonality on disease dynamics," said co-author Gabriel Vecchi, Princeton professor of geosciences and the High Meadows Environmental Institute.

The researchers used an epidemiological model based on historic RSV data and observations of the recent decline in RSV cases to examine the possible impact of COVID-19 NPIs on future RSV outbreaks in the United States and Mexico.

They found that even relatively short periods of NPI measures could lead to large future RSV outbreaks. These outbreaks were often delayed following the end of the NPI period, with peak cases projected to occur in many locations in winter 2021-22. "It is very important to prepare for this possible future outbreak risk and to pay attention to the full gamut of infections impacted by COVID-19 NPIs," Baker said.

The authors also considered the implications of COVID-19 NPIs for seasonal influenza outbreaks and found results qualitatively similar to RSV. The dynamics of influenza are much harder to project due to viral evolution, however, which drives uncertainty over future circulating strains and the efficacy of available vaccines.

"For influenza, vaccines could make a big difference," Baker said. "In addition, the impact of NPIs on influenza evolution is unclear but potentially very important."

"The decrease in cases of influenza and RSV -- as well as the possible future increase we project -- is arguably the broadest global impact of NPIs across a variety of human diseases that we've seen," said co-author Bryan Grenfell, the Kathryn Briger and Sarah Fenton Professor of Ecology and Evolutionary Biology and Public Affairs, who is associated faculty in HMEI.

"NPIs could have unintended longer-term impacts on the dynamics of other diseases that are similar to the impact on susceptibility we projected for RSV," he said.

A similar effect of pandemic-related NPIs on other pathogens was observed following the 1918 influenza pandemic. Historic measles data from London show a shift from annual cycles to biennial outbreaks following a period of control measures implemented at that time.

Co-author C. Jessica Metcalf, associate professor of ecology and evolutionary biology and public affairs and an associated faculty member in HMEI, said that directly evaluating the associated risks of NPIs by developing and deploying tools such as serology that would better measure susceptibility is an important public health and policy direction. "The future repercussions of NPIs revealed by this paper hinge on how these measures change the landscape of immunity and susceptibility," Metcalf said.

Additional authors on the paper include Wenchang Yang, an associate research scholar in geosciences, and Sang Woo Park, a Ph.D. candidate in ecology and evolutionary biology.

Many of the authors are affiliated with the Climate Change and Infectious Disease initiative funded by HMEI and the Princeton Institute for International and Regional Studies (PIIRS). The current study built on work by the same team published in December 2019 that examined how climate conditions affect RSV outbreaks in the US and Mexico. Another study by the team, published earlier this year, evaluated the impact of the climate and susceptibility on the trajectory of the COVID-19 pandemic.

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For vampire bats, social distancing while sick comes naturally

 

Common vampire bats

New research shows that when vampire bats feel sick, they socially distance themselves from groupmates in their roost -- no public health guidance required.

The researchers gave wild vampire bats a substance that activated their immune system and made them feel sick for several hours, and then returned the bats to their roost. A control group of bats received a placebo.

Data on the behavior of these bats was transmitted to scientists by custom-made "backpack" computers that were glued to the animals' backs, recording the vampire bats' social encounters.

Compared to control bats in their hollow-tree home, sick bats interacted with fewer bats, spent less time near others and were overall less interactive with individuals that were well-connected with others in the roost.

Healthy bats were also less likely to associate with a sick bat, the data showed.

"Social distancing during the COVID-19 pandemic, when we feel fine, doesn't feel particularly normal. But when we're sick, it's common to withdraw a bit and stay in bed longer because we're exhausted. And that means we're likely to have fewer social encounters," said Simon Ripperger, co-lead author of the study and a postdoctoral researcher in evolution, ecology and organismal biology at The Ohio State University.

"That's the same thing we were observing in this study: In the wild, vampire bats -- which are highly social animals -- keep their distance when they're sick or living with sick groupmates. And it can be expected that they reduce the spread of disease as a result."

The study was published today (Oct. 27, 2020) in the journal Behavioral Ecology.

Ripperger works in the lab of co-lead author Gerald Carter, assistant professor of evolution, ecology and organismal biology at Ohio State. The two scientists and their co-author on this paper, University of Texas at Austin graduate student Sebastian Stockmaier, are also affiliated with the Smithsonian Tropical Research Institute in Panama.

Carter and Ripperger have partnered on numerous studies of social behavior in vampire bats. Among their previous findings: Vampire bats make friends through a gradual buildup of trust, and vampire bat moms maintained social connections to their offspring even when both felt sick.

For this work, the researchers captured 31 female common vampire bats living inside a hollow tree in Lamanai, Belize. They injected 16 bats with the molecule that induced the immune challenge -- but did not cause disease -- and 15 with saline, a placebo.

After returning the bats to their roost, the scientists analyzed social behaviors in the colony over three days, including a "treatment period" from three to nine hours after the injections during which the researchers attributed behavior changes to the effects of treated bats feeling sick.

"We focused on three measures of the sick bats' behaviors: how many other bats they encountered, how much total time they spent with others, and how well-connected they were to the whole social network," Carter said.

On average, compared to control bats, the sick bats associated with four fewer groupmates over the six-hour treatment period and spent 25 fewer minutes interacting per partner, and the time any two bats spent near each other was shortest if the encounter involved at least one sick bat.

"One reason that the sick vampire bats encountered fewer groupmates is simply because they were lethargic and moved around less," Carter said. "In captivity, we saw that sick bats also groom others less and make fewer contact calls. These simple changes in behavior can create social distance even without any cooperation or avoidance by healthy bats. We had previously studied this in the lab. Our goal here was to measure the outcomes of these sickness behaviors in a natural setting.

"The effects we showed here are probably common in many other animals. But it is important to remember that changes in behavior also depend on the pathogen. We did not use a real virus or bacteria, because we wanted to isolate the effect of sickness behavior. Some real diseases might make interactions more likely, not less, or they might lead to sick bats being avoided."

Although the study did not document the spread of an actual disease, combining the social encounter data with known links between exposure time and pathogen transmission allows researchers to predict how sickness behavior can influence the spread of a pathogen in a social network.

Clearly identifying each bat's behavior in the colony's social network was possible only because the proximity sensors -- miniaturized computers that weigh less than a penny and fall off within a week or two -- took measures every few seconds of associations involving sick or healthy bats or a combination of the two. Visualizations of the proximity sensors' recordings showed growth in the number of connections made in the colony's social network from the treatment period to 48 hours later.

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COVID-19 study links strict social distancing to much lower chance of infection

 

People social distancing concept

Using public transportation, visiting a place of worship, or otherwise traveling from the home is associated with a significantly higher likelihood of testing positive with the coronavirus SARS-CoV-2, while practicing strict social distancing is associated with a markedly lower likelihood, suggests a study from researchers at the Johns Hopkins Bloomberg School of Public Health.

For their analysis, the researchers surveyed a random sample of more than 1,000 people in the state of Maryland in late June, asking about their social distancing practices, use of public transportation, SARS-CoV-2 infection history, and other COVID-19-relevant behaviors. They found, for example, that those reporting frequent public transport use were more than four times as likely to report a history of testing positive for SARS-CoV-2 infection, while those who reported practicing strict outdoor social distancing were just a tenth as likely to report ever being SARS-CoV-2 positive.

The study is believed to be among the first large-scale evaluations of COVID-19-relevant behaviors that is based on individual-level survey data, as opposed to aggregated data from sources such as cellphone apps.

The results were published online on September 2 in Clinical Infectious Diseases.

"Our findings support the idea that if you're going out, you should practice social distancing to the extent possible because it does seem strongly associated with a lower chance of getting infected," says study senior author Sunil Solomon, MBBS, PhD, MPH, an associate professor in the Bloomberg School's Department of Epidemiology and an associate professor of medicine at Johns Hopkins School Medicine. "Studies like this are also relatively easy to do, so we think they have the potential to be useful tools for identification of places or population subgroups with higher vulnerability."

The novel coronavirus SARS-CoV-2 has infected nearly 27 million people around the world, of whom some 900,000 have died, according to the World Health Organization. In the absence of a vaccine, public health authorities have emphasized practices such as staying at home, and wearing masks and maintaining social distancing while in public. Yet there hasn't been a good way to monitor whether -- and among which groups -- such practices are being followed.

Solomon and colleagues, including first author Steven Clipman, a PhD candidate in the Bloomberg School's Department of International Health, quickly accessed willing survey participants via a company that maintains a large nationwide pool of potential participants as a commercial service for market research. The 1,030 people included in the study were all living in Maryland, which has logged more than 113,000 SARS-CoV-2 confirmed cases and nearly 3,700 confirmed deaths, according to the Maryland Department of Health.

The researchers asked the survey participants questions about recent travel outside the home, their use of masks, social distancing and related practices, and any confirmed infection with SARS-CoV-2 either recently or at all.

The results indicated that 55 (5.3 percent) of the 1,030 participants had tested positive for SARS-CoV-2 infection at any time, while 18 (1.7 percent) reported testing positive in the two weeks before they were surveyed.

The researchers found that when considering all the variables they could evaluate, spending more time in public places was strongly associated with having a history of SARS-CoV-2 infection. For example, an infection history was about 4.3 times more common among participants who stated that they had used public transportation more than three times in the prior two weeks, compared to participants who stated they had never used public transportation in the two-week period.

An infection history also was 16 times more common among those who reported having visited a place of worship three or more times in the prior two weeks, compared to those who reported visiting no place of worship during the period. The survey did not distinguish between visiting a place of worship for a religious service or other purposes, such as a meeting, summer camp or meal.

Conversely, those who reported practicing social distancing outdoors "always" were only 10 percent as likely to have a SARS-CoV-2 history, compared to those who reported "never" practicing social distancing.

An initial, relatively simple analysis linked many other variables to SARS-CoV-2 infection history, including being Black or Hispanic. But a more sophisticated, "multivariable" analysis suggested that many of these apparent links were largely due to differences in movement and social distancing.

"When we adjusted for other variables such as social distancing practices, a lot of those simple associations went away, which provides evidence that social distancing is an effective measure for reducing SARS-CoV-2 transmission," Clipman says.

The data indicated a greater adoption of social distancing practices among some groups who are especially vulnerable to serious COVID-19 illness, suggesting that they were relatively aware of their vulnerability. For example, 81 percent of over-65 participants reported always practicing social distancing at outdoor activities, while only 58 percent of 18-24 year olds did so.

The results are consistent with the general public health message that mask-wearing, social distancing, and limiting travel whenever possible reduce SARS-CoV-2 transmission. The researchers suggest, though, that studies such as these, employing similarly rapid surveys of targeted groups, could also become useful tools for predicting where and among which groups infectious diseases will spread most quickly.

"We did this study in Maryland in June, and it showed among other things that younger people in the state were less likely to reduce their infection risk with social distancing -- and a month later a large proportion of the SARS-CoV-2 infections detected in Maryland was among younger people," says Solomon. "So, it points to the possibility of using these quick, inexpensive surveys to predict where outbreaks are going to happen based on behaviors, and then mobilizing public health resources accordingly."

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What are you looking at? 'Virtual' communication in the age of social distancing

From health care to education to media, social distancing across the globe due to coronavirus (COVID-19) has created the need to conduct business "virtually" using Skype, web conferencing, FaceTime and any other means available. With this expansive use of mobile and video devices, now more than ever, it is important to understand how the use of these technologies may impact communication. But are all forms of online communication alike?

In a first-of-its-kind study, neuroscientists from Florida Atlantic University demonstrate that a person's gaze is altered during tele-communication if they think that the person on the other end of the conversation can see them. People are very sensitive to the gaze direction of others and even 2-day-old infants prefer faces where the eyes are looking directly back at them. The phenomenon known as "gaze cueing," a powerful signal for orienting attention, is a mechanism that likely plays a role in the developmentally and socially important wonder of "shared" or "joint" attention where a number of people attend to the same object or location. The ability to do this is what makes humans unique among primates.

Throughout almost all of human history, conversations were generally conducted face-to-face, so people knew where their conversational partner was looking and vice versa. Now, with virtual communication, that assumption no longer holds -- sometimes people communicate with both cameras on while other times only the speaker may be visible. The researchers set out to determine whether being observed affects people's behavior during online communication.

For the study, published in the journal Attention, Perception & Psychophysics, co-authors Elan Barenholtz, Ph.D., an associate professor of psychology, a member of the Center for Complex Systems and Brain Sciences in FAU's Charles E. Schmidt College of Science and a member of FAU's Brain Institute (I-BRAIN), and Michael H. Kleiman, Ph.D., a postdoctoral researcher at FAU, compared fixation behavior in 173 participants under two conditions: one in which the participants believed they were engaging in a real-time interaction and one in which they knew they were watching a pre-recorded video.

The researchers wanted to know if face fixation would increase in the real-time condition based on the social expectation of facing one's speaker in order to get attention or if it would lead to greater face avoidance, based on social norms as well as the cognitive demands of encoding the conversation.

Similarly, they wanted to know where participants would fixate on the face. Would it be the eyes more in the real-time condition because of social demands to make eye contact with one's speaker? Or, in the pre-recorded condition, where the social demands to make eye contact are eliminated, would participants spend more time looking at the mouth in order to encode the conversation, which is consistent with previous studies showing greater mouth fixations during an encoding task.

Results of the study showed that participants fixated on the whole face in the real-time condition and significantly less in the pre-recorded condition. In the pre-recorded condition, time spent fixating on the mouth was significantly greater compared to the real-time condition.

There were no significant differences in time spent fixating on the eyes between the real-time and the pre-recorded conditions. These findings may suggest that participants are more comfortable looking directly at the mouth of a speaker -- which has previously been found to be optimal for encoding speech -- when they think that no one is watching them.

To simulate a live interaction, the researchers convinced participants that they were engaging in a real-time, two-way video interaction (it was actually pre-recorded) where they could been seen and heard by the speaker, as well as a pre-recorded interaction where they knew the video was previously recorded and therefore the speaker could not see their behavior.

"Because gaze direction conveys so much socially relevant information, one's own gaze behavior is likely to be affected by whether one's eyes are visible to a speaker," said Barenholtz. "For example, people may intend to signal that they are paying more attention to a speaker by fixating their face or eyes during a conversation. Conversely, extended eye contact also can be perceived as aggressive and therefore noticing one's eyes could lead to reduced direct fixation of another's face or eyes. Indeed, people engage in avoidant eye movements by periodically breaking and reforming eye contact during conversations."

There was a highly significant tendency for participants engaging in perceived real-time interaction to display greater avoidant fixation behavior, which supports the idea that social contexts draw fixations away from the face compared to when social context is not a factor. When the face was fixated, attention was directed toward the mouth for the greater percentage of time in the pre-recorded condition versus the real-time condition. The lack of difference in time spent fixating the eyes suggests that the additional mouth fixations in the pre-recorded condition did not come at the cost of reduced eye fixation and must have derived from reduced fixations elsewhere on the face.

Comparisons between total fixation durations of the eyes versus the mouth were calculated for both the real-time and pre-recorded conditions, with the eyes of both conditions being significantly more fixated than the mouth. Gender, age, cultural background, and native language did not have an influence on fixation behavior across conditions.

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