Manchester United boss Sir Alex Ferguson must rethink his plans for Sunday's Community Shield, after revealing Wayne Rooney has a virus which could force him to miss the start of the season.

United could now step up their attempts to sign a new striker, although they are also hoping to secure a work permit for Angolan front man Manucho.

Ferguson claimed on Tuesday that winger Cristiano Ronaldo is certain to stay at Old Trafford for the coming season - despite the interest from Real Madrid, whose signing of Rafael van der Vaart from Hamburg may have been a cut-price alternative to launching a world-record bid for the United star.

Injured Ronaldo is a certain absentee for this weekend's clash with FA Cup winners Portsmouth, but the loss of Rooney to illness was unexpected and leaves Ferguson short of options.

The England striker returned from the Red Devils' pre-season tour of Africa with the virus and is struggling to shake it off in time to be considered for either Sunday's game or United's Barclays Premier League opener against Newcastle the following weekend.

Ferguson told United's official website: "I doubt we'll get Rooney fit for the start of the season with the virus he's had.

"It's a virus he picked up in Nigeria and it's not a nice one, but quite a few have had it.

"It's such a bad virus, and he's got to be training to be fit."

Ferguson confirmed that Rooney was not suffering from malaria, which the entire squad had been treated against before the trip.

Carlos Tevez and the seemingly out-of-favour Louis Saha, linked with Sunderland, are the only established strikers fit and available to United - so there could be a role for 20-year-old Fraizer Campbell.

Although Real Madrid have not ruled out making a formal bid for Ronaldo, Ferguson is eager to put a full stop on the summer-long transfer saga involving his most valuable player.

He said: "The matter is closed now. He [Ronaldo] is a Manchester United player - it's finished. He'll be playing here next season, believe me. It's finished."

Real Madrid president Ramon Calderon unveiled his latest Dutch star on Tuesday, and said: "Rafael van der Vaart is the first and possibly the only signing of the summer for Real Madrid.

"We believe that this squad is full of quality, and plenty of talent."

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