Sewage Data As A Surprising Predictor For COVID-19 Cases

You might not think much of them, but bodily fluids offer a treasure trove of information for medical diagnoses. Indeed, scientists are now looking past the drain and directly into sewage to gather data about COVID-19. 

You might not have heard about it, but it turns out it is possible to detect and measure the amount of virus DNA in sewage samples which can predict case number by about 7-10 days in advance. Several countries are already employing this method to predict infection cases; and it is yet another example of an unusual association between a data source and outcomes. Combining the information gathered from such analyses with other epidemiological data, contact tracing and social media data can create the most reliable forecast system to date.

Let’s (metaphorically) dive into the sewage world, and analyse how its data paves the way for the ultimate combined predictor for COVID-19 infections.

Poop and COVID-19

SARS-CoV-2 is known to cause gastrointestinal (GI) symptoms since the virus can enter the GI tract. There, it loses its outer protein layer, but its RNA material passes through the tract intact and is “shed” in faeces. This is all flushed down the drain and collected as sewage. Now, the question that arises is whether one can get infected if in contact with such wastewater. The CDC’s answer is that “there is no information to date that anyone has become sick with COVID-19 because of direct exposure to treated or untreated wastewater.”

So far so good; but the real interest of SARS-CoV-2’s genetic material in poop lies in the fact that it is present even before typical symptoms show. And it not only applies before symptoms show but also to those infected but who remain asymptomatic but can still transmit the virus. A recent review found that asymptomatic persons “seem to account for approximately 40% to 45% of SARS-CoV-2 infections, and they can transmit the virus to others for an extended period, perhaps longer than 14 days.”

Analysing sewage for COVID-19 material can thus quite accurately forecast the number of infected cases in advance and help take preventive measures. The 7-10 days window relates to when symptoms manifest in these pre-symptomatic people. Only then do they undergo testing, receive the results and finally register as officially positive in the database. On the other hand, viral material appears in faeces within three days of infection.

Source: https://sluggerotoole.com/

Analysing this content puts detection on the fast track and is drawing the attention of public health experts. This is shaping what can be termed as “sewage epidemiology.” Let’s see how it’s done.

How to find COVID-19 in wastewater

In the U.S. alone, municipal sewage collection systems serve around 80% of households. Sewage testing can thus prove to be an effective early detection method. It can additionally help better focus testing and treatment efforts. This insight that sewage provides data regarding novel coronavirus infections is attracting public health authorities.

Source: https://www.aquatechtrade.com/

To visualise the process, let’s take an example coming from the U.S. itself. In New Haven city, Yale University researchers analyse sewage samples collected from a treatment plant. More specifically, they collect sewage sludge, or the concentrated material obtained after the processing of sewage. This sludge undergoes analysis for its SARS-CoV-2 RNA levels and reported to the city once a week. 

By comparing the virus level in the sludge with the reported number of cases in the city, the researchers found that the viral load had risen about a week before the reported cases did.

Going global

Sewage analysis for COVID-19 detection is not a pilot project in New Haven city. It’s happening in several U.S. cities. And it’s not just the U.S. but also other countries like Hungary, France, the U.K. and Spain are analysing the information contained in wastewater. Even your country might have such data in the local sewage system and could help you plan ahead. Indeed, this information is much better at predicting case numbers than futurists and public health experts together. It’s no wonder that "sewage epidemiology" is gaining traction among public health authorities.

As Dr. Andrew Singer puts it: "The earlier you find [a signal], the earlier an intervention can happen." Dr. Singer is the lead researcher in the U.K.'s Centre for Ecology and Hydrology project. They aim to develop a standardised test to assess the virus levels in a wastewater sample.

Source: https://www.sarahatherton.org.uk/

"By sampling wastewater at different parts of the sewerage network, we can gradually narrow an outbreak down to smaller geographical areas, enabling public-health officials to quickly target interventions in those areas at greatest risk of spreading the infection," said Dr. Singer. 

"It seems obvious that we should be doing this," added Dr. Singer. "But it's an approach that's never been considered for an active outbreak."

This geographical approach is a promising one and can be coupled with a COVID-19 alert system. It could even target individual buildings to inform its occupants of the need to get tested. This brings us to the ultimate combination of datasets for building a reliable forecasting system.

The ultimate combination for COVID-19 predictions

While wastewater analysis appears to offer a strong case as a reliable predictor for infected cases, its reliability can be enhanced by combining the data it offers with that from other sources. Such a combination would include datasets from traditional sources; as well as those obtained from new technologies that have gained traction during the pandemic.

As such, a likely option for this ultimate solution will be a combination of the following:

• Standard epidemiological data
• Self-reported data through contact tracing apps
• Social media analyses
• Sewage data

Sewage data can contribute to forecasting outbreaks.

Standard epidemiological data is the one that has been more prominent and relates to the officially reported cases. It can serve as a baseline for comparison purposes. Contact tracing apps gained traction during the pandemic and can better help in finding those who potentially contracted the virus at a quicker pace. Social media analyses could also give insights into demographic trends and narrow down clusters of infection zones. The latter two components inevitably raise privacy concerns, so anonymised data collection must be favoured for these purposes.

Adding sewage data to the mix will enhance the forecasting accuracy by analysing the trends and recommending increased testing in specific areas. "We can count how much virus is in a sample," explained Prof. David Graham, who is part of the team developing the U.K.’s standardised test. “And, because each sample comes from a wastewater network that serves a specific community, we can also tell you an approximate number of humans from which it came."

After fine-tuning, the scientists working on the project plan to integrate this test into a COVID-19 alert system. They could couple it with data from the suggested ultimate combination for a more robust system. Going further, since we’re dealing with data, we could augment such a system with an A. I.-based algorithm to analyse and determine trends faster from the load of data.

New solutions, new troubles

While you might now have a different outlook on what goes down the drain, some issues still need to be tackled in poop world’s data. Some of the earlier issues were with the data itself. One such analysis in Barcelona suggested the presence of COVID-19 in March 2019. That’s one whole year before the WHO declared the pandemic and 10 months before the first reported case in Wuhan. However, while more in-depth analysis of this case must be done. Experts suggest that this result is due to laboratory contamination.

As such, it raises the need to maximise accuracy with this method and explore how other contaminants can affect the results. There’s also the issue of the turnaround time. Carmel city in the U.S. partnered with biotech company Biobot to analyse its sewage samples but experienced a slow turnaround time. Time is of the essence in a pandemic. The faster we can track down where the virus is spreading, the faster we can curb it.

But they are aiming to improve on this front. “Biobot’s turnaround time was slow through March and April because it was a free service,” a spokesperson told The Verge. “Given the high demand for this testing, we are now offering it as a paid service, which started June 1st with a guaranteed turnaround of 3-7 days to start, while aiming to get it at 3 days.”

While sewage data analysis in the context of COVID-19 has room for improvement, it definitely holds potential. It has only gained traction from the public health sector recently and will improve with time. You might also want to do a quick Google search for your own country’s sewage system's website and see their data yourself. 

What’s for sure is that we will think differently of what we flush down the drain.

Dr. Bertalan Mesko, PhD is The Medical Futurist and Director of The Medical Futurist Institute analyzing how science fiction technologies can become reality in medicine and healthcare. As a geek physician with a PhD in genomics, he is a keynote speaker and an Amazon Top 100 author.

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