By Kelly A. Reynolds, MSPH, PhD

In many regions, the reopening of businesses following pandemic lockdowns have been associated with a spike in SARS-CoV-2 exposure and COVID-19 infection rates. By nature, the POU water treatment industry involves frequent interaction with personnel in manufacturing and assembly settings and consumers in households and other occupational environments (i.e., hotels, healthcare facilities, restaurants, etc.). When and where contagion will spread is fraught with uncertainty, however, there are standards and best practices that can be applied to dramatically reduce adverse health risks.

Modes of transmission
SARS-CoV-2 has been shown to remain infectious in aerosols for hours and days on surfaces.1 The cycle of transmission is completed via direct inhalation and surface-to-hand-to-face contacts where the virus can invade mucous membranes of the eyes, nose and mouth. Although both aerosol and surface transmission routes are possible, most experts agree that the virus is primarily spread through large droplets.

To define the spread of SARS-CoV-2, it is necessary to first distinguish between the large droplet and airborne spread. By definition, organisms spread by the airborne route, stay suspended in the air in small respiratory droplets, known as droplet nuclei. These particles tend to also spread further distances from the source. In contrast, large droplets settle quickly from the air onto surfaces, leaving very limited time for exposure from air spaces and relating to shorter distances of spread. Although inconsistently defined, aerosols (droplet nuclei) are generally considered to be particles less than 5 µm in diameter, whereas large droplets include particles greater than 5 µm.2

Droplets may be expelled via coughing, sneezing, talking and even breathing. While asymptomatic and pre-symptomatic individuals can shed the virus, those who are symptomatic appear to expel higher concentrations of organisms into the environment. The infectious dose appears to be low, on the level of hundreds of viruses.

The 3 Ts of pandemic control
One of the greatest challenges in the COVID-19 pandemic is that 25 percent or more of infected carriers have no symptoms but can still spread the virus to others. Thus, in addition to encouraging sick employees to stay home, it is necessary to implement additional safety precautions. Since mid-March, health organizations have promoted an increase in following the three Ts strategy of testing, tracing and treating to slow the rate of the pandemic. This strategy has been used to stop other virus outbreaks, such as Ebola.

New testing options have been rapidly developed for SARS-CoV-2 targeting either blood, mucous or saliva. Swabs of mucous and saliva can detect active infection while blood (serology) tests can detect levels of antibodies produced as the body’s immune response to infection. Antibodies are usually detectable after about a week after virus exposure and may persist for months or years post-infection.

A benefit of testing is that positive patients can begin active isolation and help to determine with whom they may have been in contact. Many state and county health departments have active contact-tracing centers that can notify individuals and warn them that they might have been exposed to SARS-CoV-2. They can provide information on how to self-monitor and avoid contact with others for 14 days, to assure they do not develop symptoms or spread the infection to others, even in the absence of symptoms.
The final T is treating. Currently, there are no definitive treatments against COVID-19 beyond supportive therapies. Blood plasma from previously infected and recovered patients shows some promise but more research is needed to fully evaluate its efficacy. In the absence of a vaccine or treatment, environmental and population-level controls provide primary defenses.

The Pyramid of Prevention
Researchers at The University of Arizona compiled a re-opening guide for workplaces that is summarized in the inverted prevention pyramid for reducing the risks of SARS-CoV-2 exposures (Figure 1).3

Key strategies include: Practice six-foot distancing, at least. This recommendation was based on the assumption that large droplets are the primary transmission route and settling of dispersed viruses would happen close to the infected source. Growing evidence, however, suggests that aerosols may also play a significant role and that the six-foot distance should be extended, especially within indoor environments.4 Gatherings should be limited to less than 10 people. Minimize communal gathering areas. When possible, allow employees to work from home. Low-density occupancy may help to reduce the overall bio-burden in enclosed spaces.

controls may be engineered into the workplace. Increasing ventilation, a common strategy in healthcare environments, is the utilization of air change rates to increase fresh-air ratios and dilute contaminants. Physical barriers are other passive controls that can help to minimize droplet spread.

Administrative controls are important actions as well. Staggering schedules, supporting the use of sick days, creating emergency communication plans, encouraging self-monitoring and creating a culture where hygiene practices are valued and rewarded can help to sustain a healthy workforce. Place hand-sanitizing stations throughout the workplace or provide travel-size products for workers in the field. Provide disinfecting wipes and tissues and use no-touch trash cans. Establish a routine for disinfecting high-touch surfaces such as door knobs, elevator buttons, phones, kitchen areas and keyboards.

Individual protective measures, such as the use of hand sanitizers, surface disinfectants and face coverings can be very effective at reducing health risks but are often listed as the least effective control measures, due to the potential for improper use or lack of maintenance. Face cloths should be minimally handled and washed daily.

Further, there is a difference between personal protective equipment (PPE), designed to protect the wearer from exposure, as compared to personal comfort face coverings that are intended to minimize the wearer’s contribution of viruses in the environment. PPE should be reserved for healthcare personnel to maximize their protection against known exposures while working with symptomatic patients. PPE should also be prioritized for high-risk populations, including immunocompromised and elderly persons.

Cloth face coverings (the common comfort masks) are beneficial for reducing droplet transmission. Recently, a study showed that face masks were one of the primary actions associated with reducing community transmission of SARS-CoV-2.5 Social distancing alone was not found to be sufficient for public protection.

A final word
Maximizing safety in the workplace relative to infectious agent exposures requires a multi-barrier approach. Practices detailed in the Pyramid of Prevention provide minimal guidance for avoiding exposures. Conducting a workplace or exposure assessment relative to individual behaviors and practices is a must for developing effective controls that are practical for your workplace to implement. Information regarding SARS-CoV-2 and the COVID-19 disease is rapidly expanding. For reliable information and the most recent updates, consult the CDC website:


  1. Van Doremalen N, Bushmaker T, Morris DH, et al. Aerosol and surface stability of SARS-CoV-2 as compared with SARS-CoV-1. N Engl J Med. 2020;382(16):1564-1567. DOI:10.1056/NEJMc2004973
  2. World Health Organization(WHO). Infection prevention and control of epidemic- and pandemic-prone acute respiratory infections in health care. WHO Guide. 2014:1-156.
  3. Workplace Reopening Guide. Mel and Enid Zuckerman College of Public Health. Accessed June 19, 2020.
  4. Jayaweera M, Perera H, Gunawardana B, Manatunge J. Transmission of COVID-19 virus by droplets and aerosols: A critical review on the unresolved dichotomy. Environ Res. June 2020:109819. DOI:10.1016/j.envres.2020.109819
  5. Zhang R, Li Y, Zhang AL, Wang Y, Molina MJ. Identifying airborne transmission as the dominant route for the spread of COVID-19. Proc Natl Acad Sci. June 2020:202009637. DOI:10.1073/pnas.2009637117

About the author
Dr. Kelly A. Reynolds is a University of Arizona Professor at the College of Public Health; Chair of Community, Environment and Policy; Program Director of Environmental Health Sciences and Director of Environment, Exposure Science and Risk Assessment Center (ESRAC). She holds a Master of Science Degree in public health (MSPH) from the University of South Florida and a doctorate in microbiology from the University of Arizona. Reynolds is WC&P’s Public Health Editor and a former member of the Technical Review Committee. She can be reached via email at


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