New Zealand coach Mike Hesson said “at least two or three are down” but didn’t reveal the nature of the illness after the Black Caps’ big win over Afghanistan on Sunday.
With top spot in Group A already wrapped up, Hesson said he won’t be risking anyone ahead of the side’s last pool match against Bangladesh in Hamilton.
That includes paceman Adam Milne, who bruised his shoulder taking a catch against Afghanistan.
Hesson has named the same starting side in all five of the Black Caps’ World Cup wins so far, but admits injury and illness could force some changes.
"If guys have a niggle we won't force it with the gaps between games," he said.
"When you've got two games in 21 days (between the Australian group game on February 28 and the quarter-final on March 21) we're not going to make it one in 21 in terms of preparation.
“If these guys are fit and still performing they'll get first chance."
The Black Caps are still second favourites behind Australia with the bookies and will play either the West Indies, Ireland or Pakistan in the quarter-finals in two weeks’ time.