Curtis, who has scored five goals in six games for Portsmouth this season after joining from the Candystripes, has impressed for Noel King’s Under-21s this campaign and netted the equaliser in a 1-1 draw away to Kosovo last Friday.
However, the 22-year-old is suspended for Tuesday’s qualifier against Germany in Tallaght Stadium so he will link up with the senior squad in Poland instead.
He tweeted: “Words can’t describe how am feeling right now about getting the call up for my country it’s a dream come true.”
Ward, who earned his 50th senior cap in the defeat to Wales, has returned to Burnley with a foot injury.
Liverpool goalkeeper Caoimhin Kelleher has also left the squad following two days training in Dragon Park, Newport.
Goalkeepers: Colin Doyle (Hearts), Sean McDermott (Kristiansund BK), Darren Randolph (Middlesbrough)
Defenders: Seamus Coleman (Everton), Cyrus Christie (Fulham), Matt Doherty (Wolverhampton Wanderers), Shane Duffy (Brighton & Hove Albion), Richard Keogh (Derby County), Ciaran Clark (Newcastle United), Kevin Long (Burnley), John Egan, Enda Stevens (Sheffield United)
Midfielders: Alan Judge (Brentford), Jeff Hendrick (Burnley), Conor Hourihane (Aston Villa), Shaun Williams (Millwall), David Meyler (Reading), Daryl Horgan (Hibernian), Callum O’Dowda (Bristol City)
Forwards: Graham Burke, Callum Robinson (Preston North End), Aiden O’Brien (Millwall), Ronan Cutis (Portsmouth)