Risk of Potable Water in Buildings Unoccupied During COVID-19

Potable Water in Buildings Unoccupied During COVID-19 

Legionella is not the only concern

Risks to Potable Water in Buildings Unoccupied During COVID-19

Legionella is not the only concern

SOUTH ORANGE, NJ, July 22, 2020 — Nephros, Inc. (Nasdaq: NEPH), a commercial-stage company that develops and sells water purification products and pathogen detection systems to the medical and commercial markets, today announced the results of a study of water in buildings affected by recent COVID-19-related shutdowns.

The manuscript describing the study is available on bioRxiv. The research team collected 88 water samples from a diverse group of buildings in four geographic regions, some of which have been unoccupied during the COVID-19 pandemic. The microbial community structure of each of the samples was analyzed using the Nephros SequaPath microbial screening system.

Nephros SequaPath™, a new microbial screening system, used to evaluate 88 building water samples across four US geographic regions

Findings confirm importance of assessing microbial community structure before reoccupancy. Testing solely for Legionella is not supported by the data.

Key takeaways from the study include:

Bacterial counts in stagnant water samples from unoccupied/under-occupied buildings were as much as 1,400 times higher than in buildings with normal occupancy and water usage.

More than 50 genera (families) of bacteria known to have at least some pathogenic (i.e., disease-causing) members were were detected in approximately 60% of unoccupied building samples, compared with 35% in occupied building samples.

Many of the bacterial genera that were detected are not typically considered in water safety testing programs. Recent guidance about water safety testing prior to re-occupancy focuses almost solely on Legionella. In this study, however, Legionella was found in only about 10% of the samples and, in samples where Legionella was identified, it was not predominant.

Many office buildings and other facilities across the country have been unoccupied and under-used during the COVID-19 pandemic. When buildings are unoccupied, water in building piping systems becomes stagnant. The level of chlorine in the water (a disinfectant used to inhibit microbial growth), decreases over time and is rarely present in stagnant water. This results in conditions known to support growth of bacteria, including many known to cause disease.

“As we return to our normal routines, health and safety is surely our number one priority, ” commented Kimothy L. Smith, DVM, PhD, Nephros Vice President of Pathogen Detection Systems. “This study confirms that, following a long period of under-use, water systems in the majority of unoccupied buildings across the country may be colonized by pathogens, many of which are not considered by most published guidance. In fact, the Legionella-centric approach that is most frequently taken is not supported by the data from this study. Negative results from water tested only for Legionella are not sufficient to declare the building safe for re-occupancy, and may put people in harm’s way by creating a false sense of security. This study highlights the need for screening of the microbial community structure as an important first step in identifying pathogens of concern and determining risk-mitigation measures.”

“As we return to our normal routines, health and safety is surely our number one priority”.

Kimothy Smith

DVM, PhD — Vice President, Pathogen Detection Systems

Daron Evans, President and CEO of Nephros commented, “Legionnaires disease, caused by Legionella, is the only reportable, plumbing-associated waterborne disease. Guidance for building water heath, including microbial testing, has focused almost exclusively on Legionella. However, in the last few years, thought leaders in water and public health have expanded their scope to include other clinically significant plumbing-associated pathogens. Important new standards, such as ASHRAE 514, are addressing multiple pathogens associated with building water systems. At the cutting edge of this new, evolving approach, Nephros has developed its SequaPath and PluraPath™ systems. With streamlined 16S rRNA gene sequencing technology, SequaPath is able to test for over 20,000 different bacterial genera in near-real time, providing a simple yet powerful tool for screening the microbial community structure of water samples from buildings. The water can then be further analyzed for multiple pathogenic species of concern in SequaPath-identified genera using Nephros PluraPath, a robust qPCR-based platform. SequaPath and PluraPath systems and services are available from Nephros and our partner network.”

The authors of the study are Kimothy L. Smith, DVM, PhD, (Nephros) and Howard Shuman, PhD (University of Chicago and Manhattan College), and Douglas Findeisen (Building Water Sampling Services, LLC).


  • A pre-print of the study is here.
  • A blog post about the study is here.
  • More information about Nephros SequaPath system is here.


Nephros provided financial support for the study.

About Nephros:

Nephros is a commercial-stage company that develops and markets high-performance water purification products and pathogen detection systems for medical and commercial markets.

Nephros ultrafilters are used in hospitals, medical clinics, and commercial facilities to retain bacteria and viruses from water, providing barriers that aid in infection control for showers, sinks, and ice machines. Nephros ultrafilters are also used in dialysis centers to aid in the removal of endotoxins and other biological contaminants from water and bicarbonate concentrate in hemodialysis machines.

Nephros pathogen detection systems, including the PluraPath and SequaPath systems, provide near-real time information on bacterial genera, waterborne bacteria, and viruses to medical and water safety professionals. These products integrate Nephros ultrafilters with DNA sequencing and quantitative polymerase chain reaction (qPCR) technology.

Nephros commercial filters, including AETHER™ brand filters, improve the taste and odor of water, and reduce scale build-up in downstream equipment. Nephros and AETHER products are used in the health care, food service, hospitality, and convenience store markets.

For more information

about Nephros, please visit its website at www.nephros.com.