COLUMBIA, Mo. – Scientists are having to test for another molecule in wastewater samples for accurate results following the recent climate across the state. 

Since the spring of 2020, researchers at Mizzou have been testing wastewater for spikes of COVID-19. But when areas flood, sewer systems become overloaded, which may results.

What’s being tested now is the substance you can find in your morning coffee, your energy drink and that piece of chocolate you ate: caffeine.

It’s also in your wastewater, and with the recent rain and flooding in the St. Louis area, it’s going to be an indicator for scientists. 

“If it rains so hard that [sewers] overflow, that’s what throws us off,” said Marc Johnson, lead researcher at Mizzou for testing wastewater for COVID-19. “It significantly dilutes the signal.”

Some parts of St. Louis saw more than a foot of rainfall this week, making it hard for researchers like Johnson to test wastewater for the virus. 

“There are other times when we have wondered whether numbers are off, so we switched to a new system where we have our own internal marker to see how diluted samples have gotten,” said Johnson.

The system includes testing for caffeine, because no matter if it rains or if your street floods, you’re probably drinking the same amount. 

“You get caffeine in the sewer shed, the only reason it’s there is because people consumed it,” Johnson said. “You’re not going to find it there like in the rivers.”

Over the past year, Johnson said his lab, along with his colleague Chung-Ho Lin, have been studying what molecule in the human body is small enough, but also a good indicator. 

“It’s been mostly a research study up until now, but we started to implement it in places where the wastewater numbers or the flow rates, which is the total amount of sewer to pass through a sewer shed in a day. If the numbers are unreliable, sometimes we will use the caffeine to correct it,” Johnson said. 

Besides caffeine, the lab also tested other molecules in wastewater, like peppers. 

“This is a virus that you only find in peppers, so if you find this virus in the sewer system, it’s probably because it was from someone who consumed some peppers,” Johnson said. 

He said that indicator was too hard to rely on because depending on how many peppers a person ate in one week, that could throw it off. 

Compared to the regular testing the lab does on wastewater for COVID, which takes less than 24 hours, Johnson said it takes a few days to test for caffeine.

“Just like you can taste your orange juice and tell it’s been diluted, we can measure the caffeine in the wastewater, which will tell us whether the human contributions have been diluted,” Johnson said.

Other parts of the state are experiencing a drought. According to the U.S. Drought Monitor, more than 20 counties are in an extreme drought, including Greene, Taney, Newton, Jasper, Ozark and Polk counties. Johnson said while rain can affect results, a drought won’t. 

“When there’s a drought, people still flush as much as they did when there wasn’t a drought, so those numbers stay fairly constant,” Johnson said. 

Johnson said his lab won’t have the caffeine results from the St. Louis area until next week, but he is expecting the levels to be a lower concentration than they have been in previous weeks. 

“We will know whether the wastewater was affected by the rain because if it was, there will be less caffeine in it per cup,” Johnson said. “If the caffeine is normal, then probably it was collected before the major rain occurred. If we got collections at the same time as the rain, we could then even predict how much flowed into the river.”

Last week, Gov. Mike Parson thanked state employees for being the first in the nation to detect the virus through sewer water. Parson said it was shortly after Missouri starting testing wastewater for COVID-19 when he got a call from the Vice President, asking him how Missouri developed this idea. Since then, other states have utilized this model to prevent outbreaks. 

The Missouri Department of Natural Resources provides the wastewater treatment facilities with the kits, boxes, bags, and tubes in order for the lab to test the samples. Johnson said once they receive the data, within a matter of hours, they upload the information to DHSS who then passes it along to local health departments. 

Johnson said that his lab at Mizzou collects roughly 150 samples of wastewater weekly from around the state. Since March, he said there has been a weekly increase of COVID in the samples. According to the Department of Health and Senior Services (DHSS), there were nearly 13,000 new cases in the past week. 

“It’s mostly BA 5, but there are still others around like BA 4,” Johnson said. “Overall, it’s been about a 20% increase each week over the week before since March. I keep thinking it’s going to crest any minute now, but it’s a wave in slow motion.”

On DHSS’s Sewershed Surveillance Project website, red triangles, meaning there’s been a 40% increase of COVID found in the wastewater in the past week or the virus has increased by 25% in the last two weeks.   

For a closer look at the Missouri Sewershed Surveillance Project, click here.