The United striker picked up the virus during the pre-season tour of South Africa and only returned to training on Friday.
However, the England international striker will definately miss Sunday's Community Shield match against Portsmouth at Wembley on Sunda and is still a major doubt for the opening Premier League match of the new season against Newcastle next weekend because of a lack of fitness.
Michael Carrick, who also picked up a virus on the African tour, is however included in the squad for the Portsmouth game.