"It's important to be out of there but we need to keep this run going," warned Glenn Roeder after goals by Jermain Defoe and Frederic Kanoute secured three precious points.
"I'm very pleased with the performance especially to have kept another clean sheet and to have scored twice," he said.
Having strung together a three-match unbeaten run, the unchanged Hammers had no place for fit-again Paolo di Canio.
And as West Ham initially struggled to break down a weakened yet workmanlike Wearside side, it looked like they could have done with their inspirational Italian.
Indeed, apart from Thomas Sorensen's brave dive into Les Ferdinand's studs, the Eastenders had little to show for their early superiority.
But after Tore Andre Flo nodded over the bar, West Ham finally got the goal they had so desperately been searching for when Ferdinand nodded down for Defoe to hook home a 23rd minute opener from eight yards.
The young striker's tenth goal of the season proved to be the only highlight of an increasingly deteriorating first half that confirms the Premiership table does not lie.
Kanoute replaced Ferdinand for the start of the second half that soon saw Defoe flash inches wide while the flying Frenchman also went close.
On the hour, Defoe agonisingly rolled a shot across an empty goal and then Sorensen had to be at his most courageous in a frantic goalmouth scramble.
But midway through the half, the Sunderland keeper had no chance when Michael Carrick robbed Kevin Kilbane and invited the breaking Kanoute to calmly slot home a low ten-yard shot.
Defoe was then denied twice in quick succession as West Ham - task completed - threatened to swamp a sorry Sunderland side bedazzled by Joe Cole's showboating.
"It's looking desperate," admitted McCarthy, clearly relieved to have kept the Hammers' advantage down to just two goals.
"I can't take any positives from today. This was a difficult task now made more difficult by two defeats in two games. West Ham were worthy winners."