Arsenal saw their lead at the top of the table cut to two points as Robin van Persie's first-half header proved enough for United to extend an unbeaten home record against the north London giants that dates back to 2006.
That Van Persie scored from a corner only underlined the absence of Per Mertesacker who, along with Tomas Rosicky, was ruled out of the Old Trafford clash completely.
Others played despite suffering the after-effects of the problem.
Yet Wenger declined to make any excuses for his side's first reverse since the opening day of the season.
"A virus can happen the whole season, it doesn't mean you have to lose the game," said Wenger.
"The players declared themselves fit. When they play, they play.
"There is no excuse."
Instead, Wenger cited a nervousness in his team during the crucial opening stages for handing United an initiative they could not wrest back despite dominating territorially in the second half.
"Until the end we looked like we can score but we lacked that quality in our final ball and the sharpness maybe to finish crosses," said the Frenchman.
With Chelsea needing an injury-time equaliser to claim a point at home to West Brom, Tottenham losing on home soil to Newcastle and Manchester City suffering yet another away defeat, this time at Sunderland, the Premier League is turning into the most unpredictable of affairs.
This inconsistency, coupled with Southampton's presence in a Champions League slot has led to accusations of a sub-standard competition.
It is not a view Wenger agrees with.
"I don't know about that," he said.
"Southampton are close to the top, but they have three players in the England squad.
"In addition, Luke Shaw is not far away and they say (Nathanial) Clyne is the same.
"Maybe the whole quality of the Premier League has gone up.
"I don't think necessarily players like Van Persie are not as good as last season or two seasons ago."