Ioane's diagnosis is unrelated to the earlier case of mumps suffered by centre Jack Goodhue, which forced him to delay his departure for New Zealand’s month-long European tour.
But coach Steve Hansen said he was not concerned about an outbreak of the virus in the All Blacks camp.
"The doc has done a great job, and we've isolated him (Ioane), so we're not worried about it spreading," he told reporters on Monday.
"It's unrelated to Jack Goodhue's because they haven't been in contact, but it has obviously come out of Auckland somewhere.”
The 20-year-old Ioane has scored eight tries in eight tests this year and become one of the world champions’ major attacking weapons.
"It'll be touch and go though if is available (on Saturday). We'll just have to see how well he comes through the week,” added Hansen.
The world champions meet the French at the Stade de France on Saturday, then play a French XV in Lyon on Nov. 14 before concluding their tour with tests in Scotland and Wales.
New Zealand got their European tour off to a winning start when a second-string side beat the Barbarians 31-22 at Twickenham on Saturday.
(Reporting by Mark Gleeson,; Editing by Ed Osmond)
