Mumps has been revealed as the mystery illness that struck down a host of Brumbies players and staff last week.
The Brumbies were forced into late team changes last Saturday night because of the spread of the illness, with Darcy Swain and Irae Simone withdrawn on the day of the game.
That duo were far from the only ones who were struck down with the virus, the cause of which remained a mystery for much of last week.
Despite the spate of illness within the team, tests conducted last week returned inconclusive.
Speaking after Saturday night's game against the Highlanders, coach Dan McKellar said it was still unclear exactly what the issue was.
Further testing this week revealed that it was mumps, and the club moved to ensure that all players, staff and their families have been vaccinated against the disease.
Rugby Australia released a statement late on Wednesday saying that tests had confirmed the diagnoses but that the outbreak was being managed.
Only players and staff who have been declared completely well, that is their symptoms have resolved and they have been isolated for at least five days, will be cleared to travel on Thursday morning.
Any players who report symptoms before take-off would be held back from travelling.
if any player or staff member becomes unwell in New Zealand, they will be immediately isolated.
While this week's selections are not expected to be impacted to the same extent as last week's, it is believed the disease will still impact the makeup of the team for the clash.
The three teams the Brumbies have faced this season - the Reds, Highlanders and Rebels - are being monitored but are yet to report any cases.
The Brumbies fly to Hamilton on Thursday morning, before taking on the Chiefs on Saturday night.