West Ham won their fourth successive Premier League game to add to Fulham's woes at Craven Cottage on Saturday, beating their London rivals 2-0 thanks to goals from Robert Snodgrass and Michail Antonio.
Fulham, yet to keep a clean sheet this season, remain rooted to the bottom of the table with nine points from 17 games, while the Hammers rose to ninth on 24 points.
New Fulham manager Claudio Ranieri had been looking to build on the four points his side had taken from their first two home games under his leadership.
His players created most of the early pressure, with strikers Andre Schurrle and Aboubakar Kamara firing in shots and creating chances within the opening 10 minutes.
But it was Manuel Pellegrini's visitors who took the lead after 17 minutes when midfielder Felipe Anderson sprang past Fulham's Denis Odoi and fed the ball to Snodgrass, who blasted his left-footed shot high into the top left corner.
Anderson helped West Ham double their lead 12 minutes later, crossing to Javier Hernandez, who nodded the ball back for Antonio to bring it down and slot past keeper Sergio Rico.
West Ham have won every game in December, their best run in the Premier League since February 2014.
"In the first half, you create a few chances against a team like Fulham, who are scrapping for points, you have to take them and we did," Snodgrass said.
"It was a great performance, and four wins on the bounce is always good."
Ranieri was philosophical in defeat but knows Fulham's fortunes will have to turn soon if they are to avoid an instant return to the Championship.
"We have to stay calm, reflect and try to work harder, harder and harder," he said.
"In a bad moment, it is important to stay together. We have a very good group, I'm sure we will react soon."