Ballard practiced on Monday and skated Tuesday, but still is not ready to return to the Wild's lineup.
According to the Star Tribune's Michael Russo, Ballard may have had a case of the mumps.
"When the Wild talked with the St. Louis Blues a few weeks ago and discovered that the Blues had a number of players test positive for the mumps (originally the Blues thought it was a bacterial issue, but mumps is a virus), the team sent Ballard and [Christian] Folin to Regions to undergo a mumps test."
The St. Louis-Post Dispatch also reports the Blues have been hit hard with mumps recently.
The Center for Disease Control notes that mumps is a contagious disease that typically starts with a few days of fever, headaches, muscle aches, tiredness and loss of appetite. It is usually followed by swelling of the salivary glands.
According to Russo, Ballard had some positive and some negative tests for mumps, so doctors aren't exactly sure what Ballard had. Despite having nearly identical symptoms, Russo notes that Folin's tests were negative.
"I've asked my mom and she said I had the [mumps] vaccine, so it makes no sense," Ballard told the Star Tribune. "So that's the hard part they're trying to wrap their heads around. How would I have gotten it?"
The Wild placed both Ballard and Folin on injured reserve last week because of illness. Folin was activated on Saturday, but Ballard has remained out.
Hockey Wilderness reports that Ballard is hoping to return for the upcoming road trip, which begins on Thursday in Ottawa.