Preliminary wastewater testing shows higher rate of coronavirus in New Castle County than reported

Pictured are boxed testing kits used to collect wastewater for COVID-19-related bacteria analysis. (Submitted photo/Biobot Analytics)

NEW CASTLE — Some are asymptomatic, others may have warning signs or no access to treatment.

The coronavirus can lurk undetected, infecting a community more than is publicly known.

Emerging scientific analysis seeks to determine just how much COVID-19 actually exists within communities and predict the potential for future outbreaks.

Last week, New Castle County announced that preliminary testing indicated roughly 15,200 cases were present above the Chesapeake and Delaware Canal as of April 15.

A Biobot Analytics’ check of bacteria taken from sewers indicated approximately 15 times the published rate of confirmed, positive coronavirus tests in the county at that time, officials said.

“The true advantage of wastewater testing is that a whole population’s samples can be taken at the same time,” said New Castle County Public Works Stormwater and Environmental Program Manager Mike Harris, who initiated contact with the Massachusetts Institute of Technology startup.

Biobot said methodology was validated with the samples collected in Massachusetts when its laboratory technique was confirmed to be selectively detecting SARS-CoV-2 The work has been submitted for peer review publication.

Several other research groups have published similar findings in the Netherlands, Australia and Montana, according to Biobot.

Delaware’s largest county paid $480 for the four-week study, all for shipping cost. About five fluid ounces are needed for a test.

According to Biobot, more than 150 samples are being processed weekly, and the company plans to expand testing capacity. After an open online call at on March 23, New Castle County responded in the first week of April.

In a letter to state officials on Wednesday, Biobot President and co-founder Newsha Ghaeli estimated that the pro bono campaign is sampling wastewater representing approximately 12% of the United States population. Delaware test results and analysis were included in the 24-page presentation.

Governor’s office spokesman Jon Starkey said the letter would be reviewed. He noted that Delaware’s response to the pandemic “has been driven by the science, and by our experts at the Division of Public Health and DEMA, in consultation with our many local and federal partners.

“Those partners include the CDC, NIH, the White House task force, local mayors, members of the General Assembly and importantly the leaders of Delaware’s hospital systems statewide.”

DEMA declined comment and spokeswoman Stacey Hoffmann said “While I am sure DPH staff will review the contents of letter, we are still not able to comment as the Division of Public Health was not directly involved.”

On Friday, Sussex County spokesman Chip Guy said the county had not pursued the testing and had no plans to do so at this time. He noted that comprehensive testing would require sampling multiple municipal and county facilities.

Last week, Levy Court Administrator Michael Petit de Mange said Kent County would follow the state’s lead regarding wastewater contagion issues.

Biobot said it has partnered with the Centers for Disease Control and Prevention in providing public information about wastewater epidemiology.

During a recent webinar posted on YouTube, Biobot’s CEO Dr. Mariana Matus discussed the importance of RNA detection related to gauging the spread of coronavirus. With the information comes an increased capability to take appropriate public health measures within communities, according to Biobot.

CDC COVID-19 task force member Dr. Amy Kirby also participated in the webinar.

Further information available

The paper submitted for publication can be found at Further analysis of the results is posted at

Along with detecting the presence of SARS-CoV-2’s genetic signature, Biobot said it is able to make predictions about a variety of public health trends.

“Initially, Biobot developed technology to measure traces of drugs in sewers to help researchers analyze patterns of ongoing drug use and detect emerging public health epidemics,” the company said.

Detailed laboratory protocols have been made available open source to the scientific community online at, Biobot said.

“Our team has a high level of confidence in our laboratory methods to detect the concentration of SARS-CoV-2 in wastewater samples,” according to a statement.

“The estimated number of active cases are the result of a modeling step and, as such, should be interpreted with caution.

“The value of our estimates is providing another source of information to piece together the level of infection in a community, as well as trending data week to week to inform the impact of mitigation and opening up cities.”

When announcing the testing last week, New Castle County Executive Matt Meyer said, “We must do whatever we can to keep communities safe, and we must do it today.

“This is a data point that may help better understand the prevalence of COVID-19 in our community. Anything that helps make this invisible enemy a little more visible is welcome.

“As we monitor readings in future weeks, we hope to gain insight that will help us flatten the curve, save lives and begin preparations to safely return to work.

“We thank Biobot for this innovative partnership.”

Four-step protocol

Biobot detailed four main steps in its protocol to quantify the SARS-CoV-2 virus in sewage:

Biobot reported the four main steps in the protocol are:

• Sample pasteurization – Sewage samples are subjected to a 60-degree Celsuis heat bath over 60 minutes to inactivate coronaviruses.

• Virus concentration – Bacterial cells are removed, and a polyethylene glycol-based precipitation method is used to concentrate viruses in the sewage sample.

• Ribonucleic acid extraction – RNA is extracted, since SARS-CoV-2 virus has an RNA genome. This RNA is used to create cDNA through a reverse transcription assay.

• qPCR (technology to measure DNA) – qPCR is used to quantify the level of SARS-CoV-2 virus in the sewage sample. The virus genome is used to make a standard curve. Copies with / mL of sewage is the result.

Biobot said protocols were validated with several experiments:

• The PCR product was sent for Sanger sequencing and it was confirmed uniquely matched the SARS-CoV-2 genome.

• Samples collected at the same treatment facility back in January (before any confirmed cases) tested negative.

• Results were reproducible across days, and

• Results were reproducible in samples stored in the fridge for two weeks.


Helpful Coronavirus links

Delaware Division of Health Coronavirus Page
CDC: About the Coronavirus Disease 2019
CDC: What to do if You Are Sick
Johns Hopkins Coronavirus Resource Center
AP News Coronavirus Coverage
Reopening Delaware: Resources for Businesses
Delaware Phase 2 guidance

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