Munster captain Tadhg Beirne refused to blame a bug in the camp after the province exited the Investec Champions Cup at the Round of 16 for the second successive season.
Their clash at Northampton Saints was finely poised at half-time, 14 points apiece, but the hosts bagged two tries through replacement winger George Hendy and kept Munster scoreless in the second period to run out 24-14 winners.
Ireland lock Beirne was among those affected by illness, and was coughing after the game, but he said it was not the reason Munster had been beaten.
"People get sick, that's part of life. You just get on with it," he said.
"That happens in team environments where we’re scrumming down against each other and all that kind of stuff.
"Lads are going to pick up bugs but that’s not the reason we lost. We went out there, went toe to toe with Saints, they just got the upper hand. We’ll have to take that on the chin.
"It was a battle. You saw in the first half how tight it was and even in the second half, the game was on a knife edge for the majority of it.
"We go from having them in their 22 to all of a sudden they’re scoring. It’s moments like that we’ll look back on and be very frustrated with.
"But I can’t fault the lads’ effort. It was certainly a battle but we came out on the wrong side of it."
Munster boss Graham Rowntree said he was "Frustrated. I spoke to the lads afterwards... I keep using this expression, 'giving them presents, giving them freebies.'
"Some big moments there where they were that good on transition when we dropped the ball or made an error and they were gone.
"There were some big swings in the game where we could have scored a try if someone held a pass, we would have scored, but they won the ball back and a few phases later, they scored. So those errors, I thought we gifted them.
"I'm proud of our effort. We stuck in there, a proper game of rugby. It's not been a straightforward week in terms of availability and illness... but we rolled our sleeves up and got on with it for a big game against a great team. I'm proud of our effort but we'll sit down and look at how we don't give away those presents."
Northampton director of rugby Phil Dowson insisted it is possible for Saints to challenge on two fronts after reaching the quarter-finals, where they will face the Bulls next weekend.
They lead the Gallagher Premiership and could now progress deep into Europe, forcing Dowson to carefully manage his playing resources as they target the double.
"I think it’s feasible, but we have to keep our feet on the ground," said Dowson, who was missing England full-back George Furbank through injury.
"One of the things we’ve been blessed with is the competition within the squad. We’ve had a lot of players contributing and we left a lot of players out this week who were unlucky not to be involved.
"As we pick up bits and pieces we need to rest and rotate. It gets heavy but we’d rather be in this situation than not.
"We’re delighted. It’s the first time we’ve been in the knockout phase of Europe for quite some time.
"We knew the levels would go up, we knew the threat Munster posed and how hard they would come out of the blocks after what happened over there. We coped with that and managed to get our game on to the pitch in the second half."
England Under-20 full-back Hendy was the man of the hour, finishing a stunning team try before showing strength to break two tackles and score in the corner to drive the final nail into Munster's coffin.
"George had a good pre-season and started the season really well. Then he had a frustrating injury," Dowson said.
"The more he plays, the better he gets and he had a huge contribution today. He’s a freak of an athlete."
