Timothy LaPara: Tracing the Fate of SARS-CoV-2

Timothy LaPara and Raymond Hozalski have been working together on issues related to drinking water for over 10 years. This team of researchers was well poised to leap into action when concerns about the novel coronavirus arose. They now have two active projects related to COVID-19; both projects build on their expertise and represent a continuation of their primary research interests.
See Hozalski: Return to Safe Buildings

On June 24, 2020, Timothy LaPara was in Pope County collecting water samples from homes with private wells. He was looking for evidence of coronavirus, officially SARS-CoV-2, in a groundwater source.

LaPara and his co-investigator Raymond Hozalski investigate microorganisms in drinking water, and they were aware of an issue in the field of water resources called the fecal-to-oral transmission route, whereby human waste can enter into lakes, rivers, or groundwater (via leaky sewer lines, septic systems, spills, etc.), contaminate a water supply, and ultimately infect humans. Recent research has shown that groundwater in Minnesota and surrounding states is often contaminated with viruses that can cause illness in humans.

Other researchers have reported finding the SARS-CoV-2 virus in raw sewage, and are in fact, monitoring sewage as a means to estimate COVID-19 infection rates in cities. LaPara and Hozalski felt that if SARS-CoV-2 is in human waste, and viruses are known to contaminate groundwater, it was only a matter of time before SARS-CoV-2 makes its way into drinking water wells. Both recognized the situation as ripe for investigation. They began investigating the fate of SARS-CoV-2 in the environment as they had done with many other microorganisms. They have established protocols for analyzing the microorganisms that are present in a particular water sample, yet the SARS-CoV-2 virus was new. Before proceeding, they used published information on the SARS-CoV-2 RNA sequence to develop a method to analyze for SARS-CoV-2 in their water samples.

LaPara and Hozalski did not expect to find SARS-CoV-2 in homes supplied with treated municipal water supplies. Cities or areas that disinfect water before distribution generally have safe drinking water, free of contamination with such harmful microbes. The greatest likelihood of opportunity for the fecal-to-oral route would arise from private wells or cities that do not disinfect, but rely solely on the natural filtration of the soil and subsurface. Water in underground wells has slowly percolated through the ground, following a path LaPara likens to that of a ball dropping through a Plinko grid. Following the natural, circuitous path takes a long time, and as the water moves along many impurities are removed.

Sometimes, however, the natural filtering process can be disrupted. A crack underground could allow water containing human waste to flow directly into an aquifer without slowly percolating down through the ground and being filtered. Such a situation could allow contaminants to enter the groundwater reservoir. Once a virus enters the cool, protected, underground environment of a groundwater reservoir, it can remain viable for a long time and eventually reach a drinking water well.

So, LaPara and Hozalski set about to study the fate of SARS-CoV-2 in the environment, traveling Minnesota to gather water samples from private wells, untreated city water systems, and a few disinfected sources as “negative controls” for validation.

The researchers collected samples via outdoor hose spigots at houses representing the various types of source water. In one Pope County yard, LaPara lets the water run long enough to ensure the water is coming from the main, to avoid confusion that can come from the household environment (which can have a significant effect on water quality). He takes standard measurements for pH, temperature, and chlorine. He sterilizes the tap using a torch and attaches a membrane filter about as long as his forearm. Once the filter is set up, about 200 gallons of water are run through the filter. The residue collected in the membrane represents all of the microorganisms in the 200 gallons of water. That residue will be concentrated (a process including coagulation and flocculation) and then tested.

SARS-CoV-2 is an RNA virus, so the RNA is extracted from the sample and assays are done to identify the presence of the virus. To identify a piece of RNA, it must first be converted to the corresponding DNA before it can be copied or multiplied. This process is very similar to the diagnostic tests used to determine if an individual is infected with COVID-19. However, a nasal swab test simply determines if the virus is present. LaPara and Hozalski want to determine the number of viruses present in the water (that is, the concentration of viruses). They use a technique called quantitative PCR.

A complicating factor with SARS-CoV-2 is that it is most infectious in an aerosol form. A person may be unharmed/uninfected by drinking the water, but taking a shower with that same water could potentially lead to an infection if the virus is still viable and in high enough concentration.

The 1,000-liter samples LaPara and Hozalski draw are large compared to typical water studies (a standard assay requires around 0.1 liter). The large samples allow LaPara and Hozalski to run very sensitive tests and discover microorganisms in small concentrations. Even so, it is still unlikely to find groundwater samples that test positive for the virus, especially so soon after the outbreak began. LaPara and Hozalski obtained a “positive control” sample from other researchers who had isolated the sample from sewage in an area on the east coast that had higher rates of COVID-19 infection.

LaPara and Hozalski were able to quickly pivot their research to test for the novel coronavirus, and their work is helping to elucidate potential risks of exposure from non-disinfected water supplies. Their inspired action supports the ability of society to maintain clean and safe water supplies.

Timothy LaPara and Raymond Hozalski were able to use established protocols and build on their expertise to address a known consequence of idle buildings and address a collateral consequence of stay-at-home orders. These innovative researchers are looking beyond the immediate concerns of the COVID-19 pandemic to ensure a safe recovery for society.