JEFFERSON CITY, Mo. — Researchers in Missouri have been testing wastewater for spikes of COVID-19 for nearly three years, but could the samples also be tested for the flu? 

Missouri is reporting more than 4,000 flu cases. Normally, the state doesn’t see those numbers until late December. With the current “tripledemic,” RSV [respiratory syncytial virus], influenza and COVID-19, are there any detectors in your wastewater that could warn the state of possible spikes?

“For influenza, yeah, it’s harder to detect than SARS-CoV2, but you can still do it,” lead researcher of the wastewater program at Mizzou Marc Johnson said. “Any virus that has nucleic acid you could theoretically test for.”

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Johnson has been testing wastewater for COVID-19 for more than two years. The lead researcher at Mizzou said the state health department asked him to roll up his sleeves and try testing samples for influenza. 

“There are several groups that have been measuring influenza from wastewater and DHSS [Department of Health and Senior Services] is interested in doing that, so right now we’re really just working out the techniques,” Johnson said. 

Unlike COVID-19 and other viruses, the flu signal isn’t as strong in your waste, making it harder to detect. 

“The levels of RNA [ribonucleic acid] that are shed by flu seems to be quite a little bit lower, so it’s a little bit tricker to get accurate readings,” Johnson said. “You get secondary infections in the gut so then that virus doesn’t have to go through the stomach and small intestine which would kill most of the signal, where with the flu, it doesn’t generally cause gut infection.”

Six weeks into flu season, the Department of Health and Senior Services (DHSS) is reporting 4,016 laboratory-positive influenza cases. Last year, at this time, there were 243 lab-confirmed cases. Compared to pre-pandemic times, during the first week of November 2018, there were 983 cases. 

John said he is also prepared for a new wave of COVID cases to show up in samples in the coming weeks. 

“The last two years, if you look at the numbers starting in November, the numbers started going up even though there were no new variants moving in,” Johnson said. 

He said DHSS has not asked him to test for RSV at this time. For now, his lab is waiting to see if what they are detecting in wastewater is correlating with what doctors are finding. 

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“It was harder to [test] before because there was no flu to detect, so we’re just now at a point where we can really evaluate it whether our probes are working or not,” Johnson said. 
A spokeswoman for DHSS said for now, the testing is in the early stages and the department is waiting to see if this method of testing wastewater works before incorporating it into their system. 

Johnson said it doesn’t take any longer to test for the flu compared to COVID-19, and expects in the coming weeks to be testing every sample for both viruses. 

Over the summer, 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 started 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 100 samples of wastewater weekly from around the state.

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