Serginho already gave an example of his goal instinct after five minutes when he hit the post from close range after AaB goalkeeper Vincent Müller had made a big mistake in the build-up.
After dominating the opening stages of the match, the visitors were rewarded after just over 20 minutes, when a delivery from Serginho sailed across the box to a completely free Thomas Jorgensen, who put the visitors ahead with an easy close-range finish.
Serginho was a constant threat throughout the first half, and five minutes before the break, the agile winger doubled the visitors' lead when he twisted and turned past a couple of AaB defenders to poke the ball home.
Things didn't get much better after the break for the home side against a potent Viborg-side in attacking mode.
Yonis Njoh took over where Serginho left during off and tripled the lead after 64 minutes when he sent the ball into the roof of the net. After the goal the pace deteriorated as Viborg switched on autopilot, while AaB was more focused on limiting the damage than chasing a comeback.
Viborg's Charly Nouck put the icing on the cake in injury time when he carved through a passive AaB-reaguard and steered the ball into the net with only seconds remaining.
Thanks to the three points, Viborg can still dream of taking seventh place, which gives them access to a playoff match for European football.
AaB are in 9th place just four points ahead of Sonderjyske who are locked in the relegation zone.