We've had reports of sightings of a female coyote following walkers with dogs on the Willoughby Loop (between 5th Street and Jordan Park). It's believed there are pups in the woods. Small mammals of this sort aren't generally a risk, though they can become threatened by aggressive dogs and will protect their young. (As a reminder, dogs are required to be on leash on the entire Rivanna Trail.)
The Virginia Department of Wildlife Resources has tips for dealing with wildlife furbearers: https://dwr.virginia.gov/wildlife/urban/.