Wildlife biologists have enlisted the help of mice and other creatures as they try to better understand how viruses infect humans and how to protect them.

“Most of the emerging infectious diseases that arise come from wildlife reservoir hosts,” researcher Kurt Vandegrift said in a statement from Pennsylvania State University. The university added, “One key to fighting emerging diseases is finding out before they get into humans which pathogens we’re mostly likely to encounter — the ones that are carried by the wild creatures we’re most likely to touch, share space with, or be bitten by.” In the U.S., that includes mice and deer ticks, for example.

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While studying wildlife, the scientists may find viruses that could one day evolve to infect humans. Discovering them ahead of time gives experts a leg up on observing how the viruses work, creating vaccines or taking other measures.

Studying animals has another benefit: Learning more about their viromes — the collections of viruses in and on them — could lead to more information about the human virome.

Human beings are full of viruses, Penn State says. “Some of your viruses are just visiting and will be gone in a week. Most are permanent tenants. A few may even find their way into your DNA.” That’s not necessarily a bad thing, as the university notes that we owe our placenta and thus our reproductive process to virus genes and evolution. We can also be invaded by a virus but never see an infection, or become barely sick at all while others are debilitated.

“We are rarely, if ever, infected by just one germ at a time,” according to Penn State, “and since pathogens change your immune system, how sick you get from a new pathogen doesn’t depend only on the ones you’re infected with now; it’s a reflection of all the infectious diseases you’ve ever had, and even in what order you had them.”

The ongoing research would not be the first time animals have taught scientists a thing or two about viruses. Smallpox is now eradicated but was once a highly contagious and often deadly virus in humans. The English doctor Edward Jenner is famous for his work to end the epidemic in the late 1700s, after he had observed that “dairymaids were protected from smallpox naturally after having suffered from cowpox,” according to an article on the U.S. National Library of Medicine.

Jenner exposed an 8-year-old boy to material from lesions a dairymaid had developed due to her exposure to cowpox, then later to smallpox, finding that the cowpox had protected the boy from the latter viral infection. “Jenner decided to call this new procedure vaccination,” the article says, and it “represented the first scientific attempt to control an infectious disease by the deliberate use of vaccination.”

See also:

Will We Create the Very Virus that Ends Up Destroying Humanity?

Signs of Contagious Mumps Virus