Study: Nonpharmaceutical interventions can control or eliminate COVID-19

Multi-university modeling shows that early termination of strict social distancing could trigger devastating second wave

May 11, 2020

Editor's note: As of May 11, America’s reopening has begun, just weeks after the coronavirus had the country on lockdown. Already, more than half the states have started to reopen their economies.

Since the novel coronavirus is transmitted among people who come in close contact with each other, the implementation of strict social distancing measures has been the primary tool for curbing the spread of the pandemic. As of April 7, 2020, mandatory lockdowns or stay-at-home orders have been imposed in more than 42 states in the U.S. This represents over 95% of the U.S. population, involving approximately 316 million Americans. Enahoro Iboi Enahoro Iboi is one of the lead authors of the study and a graduate student in ASU’s School of Mathematical and Statistical Sciences. Download Full Image

Predicting the course or severity of a pandemic, such as COVID-19, as well as the realistic assessment of proposed public health intervention strategies for combating them in real time, is a major challenge to both the public health and the scientific community.

Even as government leaders tout protecting public health as a top priority, some are looking for ways to start “opening up” and loosening stay-at-home restrictions in the hopes of providing some economic stimulation. Some states are proposing guidelines starting in early May that will allow people to get haircuts or eat at dine-in restaurants if businesses limit occupancy, physically distance patrons and check employees for COVID-19 symptoms before their shifts.

The duration and timing of the relaxation of strict social distancing measures are crucially important in determining the future trajectory of the COVID-19 pandemic.

A new collaborative research study — from Arizona State University, the University of Florida Gainesville, the University of New South Wales and Harvard Medical School — shows early termination of strict social distancing measures could trigger a devastating second wave of COVID-19 with results similar to those projected before they were implemented.

The simulations show that terminating the current strict social distancing by the end of April will result in a significant rebound of COVID-19 burden in as early as July 2020.

With no vaccine yet available, efforts at containing COVID-19 are focused on what nonpharmaceutical measures will have the greatest impact on curbing the spread of the disease.

The team of researchers recently developed a new mathematical model, which may be the first of its kind, that incorporates five nonpharmaceutical interventions: social distancing, quarantine of suspected cases, isolation of confirmed cases, contact tracing and testing, and use of face masks in public.

The scientists found that use of face masks in public could lead to the effective control, or elimination, of COVID-19 in the state of New York and the entire U.S. if the coverage levels are high enough. The compliance level needed decreases if wearing face masks in public is combined with a strict social distancing strategy.

Their results also showed quarantine of suspected cases and contact tracing have only marginal impact in minimizing COVID-19 burden, measured in terms of minimizing COVID-19 hospitalizations.

The study, Mathematical assessment of the impact of nonpharmaceutical interventions on curtailing the 2019 novel Coronavirus, was published this week in the journal Mathematical Biosciences. The study was supported in part by funding from the Simons Foundation and the National Science Foundation.

The project is a collaboration with members of the PLuS Alliance, which combines the strengths of leading research universities on different continents, including Arizona State University and University of New South Wales Sydney, to develop sustainable solutions to society’s global challenges, such as global health.

One of the lead authors and a graduate student in ASU’s School of Mathematical and Statistical Sciences, Enahoro Iboi, shared his concern after hearing about the state of Arizona’s plans to reopen in May.

“Lifting the current stay-at-home orders too soon in Arizona may likely lead to a second wave in both COVID-19-related daily mortality and cumulative cases,” said Iboi.

“This is probably the first most detailed modeling study to give a robust assessment of the various lockdown relaxation scenarios in terms of number of additional mortalities we can expect,” said Arizona State Foundation Professor Abba Gumel.

“We currently have about 10,000 cases and 400 mortality, or about 4% case-fatality ratio, in the state of Arizona. I really hope they do not do what they are planning to do. It is going to cause a lot more deaths,” said Gumel. 

The researchers developed a new mathematical model for studying the transmission dynamics and control of the COVID-19 pandemic in the U.S. and in particular the state of New York, the epicenter of COVID-19.

“This study is so important because we need thorough, well-designed, informative data-driven research to guide public health action,” said Matthew Scotch, associate professor of biomedical informatics in the College of Health Solutions and assistant director of the Biodesign Center for Environmental Health Engineering at Arizona State University.

The model is a Kermack-McKendrick, compartmental, deterministic system of nonlinear equations. It incorporates features pertinent to COVID-19 transmission dynamics and control, such as the quarantine of suspected cases, the isolation or hospitalization of confirmed, contact tracing, social distancing, and the use of face masks in public. The model uses available COVID-19 mortality data, which is more reliable than case data, and provides a realistic real-time assessment and estimate of the burden of the pandemic in New York.

The researchers first used the model to simulate the impact of social distancing, which for this study included not only individuals staying six feet apart, but also closures of schools and nonessential businesses, staying at home, avoiding crowded events and large gatherings, and moving in-person meetings online.

They found that the state of New York and the entire U.S. could have faced between 100,000 to 200,000 deaths had the strict social distancing measures not been implemented in March.

The effect of the timing of when to terminate the current strict social distancing protocols was also monitored. The simulations showed that terminating strict social distancing, face mask usage, contact tracing, quarantine and isolation by the end of April will result in 144,000 deaths in New York state, representing a 37% increase, while the nation will record up to 156,000 deaths.

The study shows that early termination of the current strict social distancing measures by the end of April will result in such a catastrophic outcome it would be as if all the gains made by social distancing and other mitigation measures will essentially be lost.

However, if the strict distancing measures were not terminated until the end of May, the cumulative mortality figures are projected to be 91,800 for New York state and 118,300 for the entire U.S.

If the social distancing measures are terminated at the end of June, the projection for the cumulative mortality figures are 33,200 for New York state and 50,300 for the entire US. This represents 68% and 69% reductions, respectively, in the baseline cumulative mortality.

This study clearly shows that the clamor to “reopen” and relax or terminate the social distancing measures that have proven to be hugely successful would undoubtedly trigger a devastating rebound of COVID-19 in both New York state and the entire U.S.

Contact tracing involves searching for individuals with whom a confirmed case has closely interacted within a certain time frame, such as two days prior to the onset of symptoms, then interviewing, testing and isolating or hospitalizing that contact if they have the disease.

In this study, contact tracing is very much interlinked with testing. Contact tracing is carried out after a confirmed case is diagnosed, following testing and diagnosis.

Results show that while contact tracing is important in reducing the size of the pandemic peak number of new COVID-19 cases, investing much resources toward contact tracing beyond the baseline rate might not be cost-effective.

Simulations were further carried out to assess the impact of widespread use of masks in public. The results show a marked decrease in the number of hospitalizations, for both New York and the entire U.S., with increasing use of more effective masks and with wider coverage.

Additional simulations assessed combining the strict social distancing strategy with using a moderately effective mask. If only 30% of the residents of the state wear masks with efficacy of about 50%, the study shows that COVID-19 can be eliminated from the state of New York.

Similar results were obtained for the entire U.S., showing a mere 10% of mask-wearing compliance with a 50% efficacy mask combined with strict social distancing will be needed for COVID-19 elimination.

“Community transmission can be controlled if lockdown measures are partially lifted, as long as individuals wear a mask in public and large-scale randomized testing is done to really give us a clear assessment of where we are,” said Gumel. “And the testing is complemented with the strict containment strategy of rapidly isolating the confirmed cases and isolating their contacts.” 

“Wide-scale randomized testing will let us know if we need to stop the partial lifting of restrictions, or if we need to further relax the lockdowns.”

The study suggests that COVID-19 is a disease that appears to be controllable using basic nonpharmaceutical interventions, particularly social distancing and the use of face masks in public, especially when implemented in combinations.

The factors that are critically important to the success of the COVID-19 control efforts are the early implementation of these intervention measures and ensuring their high adherence in the community.

“The lockdown-lifting guidelines announced by the White House are actually very reasonable, but it is clear many states are rushing to reopen without even meeting the basic steps of the gating criteria,” added Gumel. “The first step is to ensure that you have a two-week downward trend in new cases. Most of the states that lifted or partially lifted the lockdown have not met this basic first step yet.”

Rhonda Olson

Manager of Marketing and Communication, School of Mathematical and Statistical Sciences


image title

Class of 2020 told, 'Be prepared to create'

May 11, 2020

Speakers at virtual commencement acknowledge this is a time of unprecedented uncertainty but remind the newest alumni that they have shown grit in finishing strong

Arizona State University celebrated its newest graduates virtually on Monday, marking the most extraordinary graduation in the history of the institution.

The half-hour recording took the place of the spring 2020 commencement ceremonies that were to be held at Sun Devil Stadium (undergraduate) and Desert Financial Arena (graduate), where thousands of students and their families were going to mark their graduation. The in-person commencement transitioned to a virtual ceremony due to the COVID-19 pandemic. ASU switched to remote learning and teaching in mid-March.

The Class of 2020, more than half of whom are Arizona residents, included about 11,200 undergraduate students (about 4,200 of those online), more than 5,000 graduate students, more than 900 military-affiliated students and more than 6,500 students graduating with honors, the largest cohort to hold that distinction. Among the newest ASU alumni were nearly 700 Starbucks College Achievement Plan graduates and five students making up the first graduating cohort of ASU's partnership with ride-share company Uber

Monday's virtual ceremony included elements of a typical commencement: “Pomp and Circumstance,” the university mace, and congratulations and encouragement for ASU’s nearly 16,400 graduates from several distinguished speakers. 

MORE: Meet notable graduates from around the university

ASU President Michael Crow thanked the students for their perseverance through uncertainty and complexity.

“This is a hugely important day. Students’ lives are moving forward,” he said. “They completed successfully their last term, their projects, their activities, engaging in hundreds of thousands of video interactions and millions of minutes of Zoom time.

“It’s been a fantastic moment of opportunity and creativity.”

Crow said that the message of the times is, “Be prepared.”

“You need to be prepared to enhance your learning. You need to be prepared to enhance your innovation capabilities. You need to enhance your voice with new ideas and new ways of getting things done. You need to be prepared to create,” he said.

“Be prepared to do what’s necessary to help us address all the complexities that our modern world confronts us with.”

Ruth McGregor, former chief justice of the Arizona Supreme Court, told the graduates that they have been tested.

“You have already demonstrated courage and the will to continue as you completed your degrees under the most unexpected and difficult circumstances imaginable,” she said.

“You are fortunate because you already know that you can overcome obstacles and continue to follow your path.”

The speakers also acknowledged the sadness of the circumstances.

Leah Jones, president of the Graduate and Professional Student Association at ASU, who is earning her PhD in sustainability, asked the graduate students to close their eyes and imagine being together at commencement.

“As we open our eyes, this image is not what surrounds us,” she said.

“We’re at home, maybe with family or maybe we’re alone. We’re preoccupied by the context of our world, by the way it’s distorted our lives and that of people around us.”

She recognized that graduates may be feeling disappointment and frustration.

“Even if you don’t feel in a celebratory mood, I encourage you to pause even for just a moment, and be proud of all that you accomplished,” she said.

School of Music student Ben Cortez recorded a new version of the ASU alma mater.

Luis Alberto Moreno, a graduate of the Thunderbird School of Global Management and the president of the Inter-American Development Bank, told the graduates that although the outlook is uncertain, they should consider the big picture.

“You have to remember that you have earned a degree at a highly respected university in what is the world’s most advanced nation,” he said. “Only the tiniest fraction of humanity has access to the kind of opportunities you have had at ASU.”

He said that the Class of 2020 is graduating at a turning point in history.

“This crisis that we’re experiencing, with all of its heartbreaking costs, might well give birth to profound social, economic and political change — changes that we can only begin to imagine,” he said.

“And the world that will emerge from this challenge will need smart, energetic and, more importantly, creative people like you to shape and to lead those changes.”

The ceremony included highlights of the past four years of the Class of 2020, including Sun Devil Welcome in August 2016, the renovations of Sun Devil Stadium and Hayden Library, Olympian Michael Phelps joining the “Curtain of Distraction,” “Hamilton” at ASU Gammage in 2018 and the rapid move of everything online this past semester. 

In addition to the virtual commencement, colleges and schools also are hosting virtual convocations on May 11-12. At those smaller ceremonies, there will be a special moment for each graduate with their name, photo, degree and a comment from them about their future.

Today’s graduates also can attend the December 2020 or May 2021 in-person commencement ceremonies if they wish. 

The end of the commencement video included a performance of the alma mater by the Devil Clefs student group, with scenes from the ASU community over the past two months: making personal protective equipment, researching the virus in labs, treating patients, collecting donations and painting the “A” blue to honor health care workers. 

Then the maroon and gold balloons dropped onscreen. 

Watch the 2020 ASU virtual commencement ceremony

Mary Beth Faller

Reporter , ASU News