Since returning from the recent Africa Cup of Nations in Gabon, the Ghanaian has netted three times in four matches, including a consolation in a 3-2 reversal to Leicester City ahead of the international break.
The 27-year-old currently has four goals in 16 appearances since his club record transfer from Swansea City in summer last year.
“He [Ayew] is an important player for us," Fonte told his club's official website.
"He’s been showing his qualities and hopefully he can keep scoring goals for us and helping, because we need him.”
Ayew's West Ham career, however, did not get off to a good start as he picked up a thigh injury on his debut against Chelsea last August.
Sidelined for almost three months, the French-born struggled for form - and indeed game time - upon his return late October.
He joined West Ham on a three-year deal worth £20.5 million after netting 12 times in 34 league outings for Swansea last season.
He has also been on the books of French clubs Marseille, Lorient and Arles-Avignon.