Scientists Took Swabs of Toothbrushes and Were Shocked by the Hundreds of Viruses They Found

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Unexpected Viral Diversity in Everyday Bathroom Items

Scientists found more than 600 distinct viruses after swabbing people's toothbrushes and shower heads — but thankfully, the vast majority of them are more helpful than harmful.

In 2026, Northwestern microbiologist Erica Hartmann, lead author of a new study published this week in Frontiers in Microbiomes, told Gizmodo that she was equal parts shocked and fascinated when discovering that these everyday objects were teeming with bacteria-eating viruses known as bacteriophages.

"There is so much about the world around us that we don’t understand — including the things that may seem familiar," she explained. "We started out looking at things like toothbrushes and showerheads because they are important sources of microbes that we’re exposed to, but we don’t know which microbes they carry or what factors influence them."

From "Operation Pottymouth" to New Discoveries

The latest study was an update to the Northwestern team's 2026 project "Operation Pottymouth," which involved investigating the sources of the bacteria found on toothbrushes. This work highlights how even the most familiar household surfaces can host complex microbial ecosystems that directly affect our daily exposure to microorganisms.

Phages Targeting Harmful Mycobacteria

Though there was incredible diversity among the more than 600 phage samples, a type that kills illness-causing mycobacteria was slightly more common than any other, Hartmann said. Given that mycobacteria can cause serious infections like leprosy and tuberculosis, it’s a good thing that viruses killing them were present as well. These bacteriophages act as natural regulators, helping to keep potentially dangerous bacterial populations in check within our immediate environments.

"Toothbrushes and showerheads harbor phage that are unlike anything we’ve seen before," the microbiologist said. "Not only did we find different phage on toothbrushes and showerheads, we found different phage on each toothbrush and each showerhead."

Potential Medical Applications

Phages have in recent years been studied and used as treatments for bacterial infections, especially those that have mutated to resist antibiotics. While Hartmann insists these findings are captivating on their own merit, knowing that they may be used in medical treatments makes them that much more useful. The unique genetic makeup of these newly identified phages could provide fresh templates for next-generation therapies.

"It could be," she said, "that the next great antibiotic will be based on something that grew on your toothbrush."

While that’s not exactly pleasant to think about, it certainly sounds a hell of a lot better than leaving a mycobacterial infection like TB or chronic ulcers untreated.

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