Mumps has again struck the All Blacks.

Bad things come in threes, and that is the case in the All Blacks camp after Hurricanes openside Ardie Savea became the third player to go down with the contagious viral illness.

Savea missed the All Blacks first field session of the week in Cardiff after the onset of the virus was identified - and he has been swiftly isolated.

It is believed Savea caught the illness from team-mate Rieko Ioane. As the rest of the squad flew out to London, rookie centre Jack Goodhue also missed that opening match against the Barbarians at Twickenham while remaining at home to recover from the mumps.

The All Blacks said at the time Goodhue did not come into contact with Ioane, and that players involved had been previously vaccinated at some stage.

Savea was unlikely to feature in the final test of the year against Wales, with Matt Todd being preferred as back up openside to Sam Cane recently.

Regardless, Savea's season has now almost certainly come to an end.

"Ardie has got a mild dose of the mumps," All Blacks assistant coach Ian Foster revealed. "He's the only one so he's in his room in isolation. He's been fully vaccinated previously as a kid but clearly he's got something. He's been in isolation for a few days. He's actually recovering pretty quickly but we've just kept him apart."

Once he became aware of the issue, All Blacks team doctor Tony Page also isolated Ioane at the backend of the week in London. But it is not known exactly when Ioane first presented symptoms, and with the team all travelling on the same flights; staying at the same hotel and players sharing rooms, there is a chance more cases could yet crop up before the end of this week.

Based on Ioane's case, this week was the danger one for others to potentially suffer from the illness.

"If you look at the timelines that's probably how it would work. Clearly it caught us on the hop a little bit," Foster said. "It's not something you get a lot of so it has come out of the blue a little bit but we're really satisfied with the way doc has reacted really quickly with Rieko and obviously Ardie was susceptible even though he's done everything right in the past.

"Are we worried about it? No. But we've taken every precaution. Clearly Ardie must have been in pretty close proximity to Rieko at some point."

For now at least, Foster did not believe anyone else had the mumps.

"They're not showing any warning signs. I'm not a doctor but it's something we've taken really seriously. We're not just sitting back taking it for granted I know Tony has done a great job of isolating it but clearly Ardie has caught something."