Mikel Arteta praised his players’ ­fortitude after a patched-up Arsenal side overcame a sickness bug in the squad to defeat Brentford and keep up the pressure on Liverpool.

Kai Havertz was forced to miss the trip to west London because of illness but goals from Gabriel Jesus, Mikel Merino and Gabriel Martinelli enabled Arteta’s side to recover from going behind to Bryan Mbeumo’s 11th league goal of the season. The ­victory leaves them six points behind the leaders, albeit from a game more, before Saturday’s visit to Brighton.

Related: Arsenal climb to second after Gabriel Martinelli rounds off win at Brentford

Arteta is hopeful that Havertz – who the Arsenal manager said was one of several players affected by the bug – will be available for the trip to the south coast. But asked whether his squad is too stretched to deal with a hectic schedule of nine matches in January, Arteta said he had faith in the players at his disposal.

“When I see the willingness of each individual to play through anything and the versatility that we can create within our idea then the answer is no,” he said. “But we don’t know if something else happens then we may have other issues. These things happen – in this period there are always throat infections and viruses. Hopefully not and we get people back like we had Ricky [Calafiori] today. We need everybody.”

Arteta gave Ethan Nwaneri his first league start more than two years after he became the youngest player in Premier League history at this ground. The 17-year-old played a part of Arsenal’s second and third goals and Arteta said he deserved his opportunity.

“In that position it wasn’t because of the bug – I made it because I thought he was the best player to play in that position at the start of the game,” he said. “And because there was a story there with him making his Premier League debut. Sometimes that feeling comes in and you think it’s the right one.”

Arsenal’s second goal, from ­Nwaneri’s corner, was the ninth they have scored from corners this season and Brentford’s manager, Thomas Frank, said they were caught out by the routine devised by Nicolas Jover, the set-piece coach who began his career in England at Brentford. “I need to look more into it, but they are very good at it and it’s something we need to learn from,” he said.