The outbreak comes days before Rangers face bitter rivals Celtic in the first Old Firm derby of the season.
Gerrard and six players were not on board the three coaches that ferried the squad and backroom staff to Glasgow airport for their flight to Armenia.
Assistant coach Garry McAllister is set to be in charge for the match which Rangers lead 1-0 after the first leg.
Rangers had confirmed the outbreak in a statement on Tuesday without divulging the names of the players and staff involved. The outbreak is hardly ideal preparation for Gerrard's side ahead of Sunday's meeting with Celtic.
It is believed, though, the rules would allow Rangers to request a postponement of the Celtic match if they have insufficient players to fulfil the fixture due to the outbreak.