“We don’t do science projects just because they’re cool. We’re doing them to solve important problems that are facing the nation and our workforce.”
So said Dr. Lloyd Hough, who leads the Department of Homeland Security (DHS) Science and Technology Directorate’s (S&T) Hazard Awareness and Characterization Technology Center (HAC-TC). HAC-TC provides subject matter expertise on chemical, biological, and explosive hazards to S&T programs and supports the directorate’s use of the innovative science-based capabilities at S&T’s National Biodefence Analysis and Countermeasure Center (NBACC) to conduct vital research on COVID-19 and other diseases.
And Hough is right—with a devastating pandemic raging around the globe, there is perhaps no more important scientific endeavor than to identify ways to stop the spread of the novel coronavirus.
Soon after the outbreak began in the U.S., S&T created a COVID-19 Master Question List (MQL) that continues to be updated weekly. The MQL attempts to quickly summarize what is known and needs to be known about the virus. Questions like: How easily does it spread? What are the signs and symptoms? What is its stability in the environment? NBACC researchers applied their unique capabilities for characterizing biological threat agents to study environmental stability so that federal government and response agencies can prepare risk models to defend the homeland.
“It is of utmost importance to know how threat agents survive on surfaces, in the air, in various temperatures and humidity levels,” said Hough. “The answers will help us learn how to stay safe.”
“This research is important to help us better understand the potential for disease transmission in different environments,” said Dr. Paul Dabisch, a senior principal investigator and Aerobiology Team lead at NBACC. “However, many factors beyond just the survival of the virus on surfaces or in aerosol particles have the potential to impact disease transmission, such as the amount of virus expelled during breathing, talking or coughing, and how much virus is needed to infect someone. All these factors need to be assessed to determine the risk of disease transmission during different activities in different environments.”
Cutting-edge technology allows scientists to recreate multiple environments in a lab
NBACC researchers began their environmental studies in March 2020, focusing on testing how resistant the coronavirus is to sunlight, heat and humidity in droplets on surfaces, and in aerosols suspended in the air. Results from the studies were published this spring and summer in the peer-reviewed Journal of Infectious Diseases and the American Society for Microbiology’s mSphere®.
“The more stable a biological threat agent is in the air, the farther downwind it will go. The same thing is true in a public health crisis, as potentially more people could be infected,” said Hough. “We have unique facilities at NBACC to do environmental stability studies on the coronavirus, including biosafety level-3 laboratory and aerosol chambers, with which to safely study the virus on surfaces and in aerosol.”
Laboratory biosafety level is defined by the hazard associated with working with different types of infectious diseases. Biosafety level 1 (BSL-1) laboratory is for benign organisms, such as non-pathogenic strains of Escherichia coli, which do not sicken healthy humans. In BSL-2 through BSL-4 laboratories, the danger and precautions increase. For the virus that causes COVID-19, Severe Acute Respiratory Syndrome Coronavirus 2 or SARS-CoV-2, researchers work in BSL-3 laboratories.
What makes NBACC unique is a special capability for studying viruses/microorganisms in different environments—an aerosol chamber with a controllable environment housed inside another specialized containment system. Inside the chamber, NBACC researchers can produce aerosols, control the temperature and humidity, add simulated sunlight, all to replicate different environments in the U.S. at different times of the year.
“We wanted to understand where this virus is most stable, so that we can focus efforts to treat the environments where the virus is most likely to be transmitted,” said Hough. “For example, this will help us advise other DHS agencies what and when they have to clean, and how we can most safely operate checkpoints and customs at the airports, so passengers can fly safely.”
NBACC scientists working with the aerosol chamber have expertise in aerobiology, like Dr. Dabisch and Dr. Shanna Ratnesar-Shumate. Aerobiology is the study of particles passively transported by the air, including pollen, spores (fungal, fern, moss), bacterial spores, miniscule insects and seeds, and, of course, viruses.
“We study infectious aerosols containing influenza, potential bioweapons like anthrax and most recently SARS-CoV-2,” Ratnesar-Shumate said.
Studies show that of all environmental factors impacting COVID-19, sunlight is key
In the recently published studies, NBACC researchers focused on how different environmental conditions affect the survival of infectious virus on surfaces and in the air.
To look at how stable SARS-CoV-2 is on surfaces, they used larger droplets of simulated saliva and respiratory fluid containing the virus. Such droplets can be generated if a person sneezes or coughs and quickly drop on the ground. The researchers placed them on metal coupons inside the aerosol chamber and observed how long the virus remains infectious when exposed to simulated sunlight. While the virus survived for prolonged periods in the dark (similar to indoor conditions), in sunlight, 90% of the virus died in minutes.
To see how stable the virus is in aerosols, the researchers produced aerosols that mimic those produced by humans when breathing, talking, or coughing. These particles remain airborne for extended periods of time and can travel significant distances.
“If people are sitting in a room and are talking, breathing, laughing, those aerosol particles are just hanging out and continuously floating and accumulating, increasing the risk of infection. Once inhaled, aerosols could reach deep into the lungs,” Ratnesar-Shumate said.
The researchers produced the aerosols with virus into the chamber at different humidity, temperature and sunlight levels. The results showed that sunlight was the strongest environmental factor that inactivated the virus, killing most of the virus in minutes.
“It was surprising that the humidity did not play a part in the aerosol study, because humidity has always had an effect on the survivability of viruses, specifically the influenza virus and even some of the other coronaviruses,” Ratnesar-Shumate said. “All environmental factors were eclipsed by the sun.”
Lessons learned from past outbreaks help inform the ongoing pandemic response
NBACC was founded in 2010 to defend the nation against biosecurity threats, such as the 2001 anthrax attacks. During the Western Africa Ebola epidemic (2013-2016), S&T prepared an MQL that helped focus S&T’s research on questions that only NBACC could answer. This experience served as a model for how to respond to future outbreaks. S&T has developed MQLs for several other bioagents of concern, such as the anthrax bacteria and the Middle East Respiratory Syndrome coronavirus, or MERS-CoV. These MQLs identify knowledge gaps that often lead to laboratory research efforts. As an example, NBACC studied how long influenza virus remains infectious in aerosols in sunlight, which facilitated current COVID-19 research.
“Our response to the COVID-19 pandemic required us to shift research priorities almost overnight, which isn’t easy,” Dabisch said. “While we were able to leverage existing methods and capabilities, the need to rapidly shift our research focus has provided insight to help us refine and streamline our planning processes and workflows, which will hopefully allow us to respond more rapidly to future outbreaks if they occur.”
Lessons learned from past outbreaks and NBACC’s recent studies are available to help guide federal, state, and local decision-makers as they continue to implement and execute their COVID-19 response plans. S&T is committed to arming stakeholders with scientific data and practical resources—like two online calculator tools (Surface Decay and Airborne Decay)—they can use on the front lines.
Additional NBACC COVID-related studies on the horizon
NBACC is continuing to focus its scientific efforts on COVID-19 studies. In addition to work with aerosols containing SARS-CoV-2, NBACC scientists are also studying decontamination methods, testing how effective different chemicals (e.g., peracetic acid, bleach, hand sanitizers, disinfectant wipes) are for indoor areas and highly touched surfaces. The scientists are also working to improve estimates of how much virus an individual might need to inhale before they get sick. These studies will produce critical data enabling informed decisions that may reduce the spread of the disease as we enter the colder months of the year that coincide with flu season. Most of these studies will continue through the fall and into the winter.
“Here at NBACC, we focus our efforts on the research questions that we are uniquely positioned to answer,” said Hough. “In the middle of a crisis, you don’t want to be developing new technologies or implementing new approaches. We focus on what we are best at.”