ILL FEELING: Kane Williamson was the worst-affected player from a virus that hit the Black Caps squad, forcing him to sit out Wednesday's training in Hamilton.

Illness prevented leading batsman Kane Williamson from training with his teammates on Wednesday as the Black Caps faced the first major off-field glitch of its Cricket World Cup campaign.

Williamson is the most-heavily affected of a handful of New Zealand players who contracted a virus after their six-wicket win over Afghanistan on Monday.

Grant Elliott and Daniel Vettori, who were also affected by the stomach bug which they may have contracted from food from a visitor to the New Zealand camp, were both able to train to some extent on Wednesday.

Fast bowler Adam Milne, who suffered a shoulder injury when tumbling to take a catch against Afghanistan, took a limited part in training and didn't bowl.

Wicketkeeper Luke Ronchi provided a graphic description of the symptoms of the illness, but said Williamson was thought likely to be fit to play in the Black Caps' final pool game against Bangladesh on Friday in Hamilton.

New Zealand has used the same 11 players in all five of its pool matches to date and has planned to continue that selection policy throughout the tournament unless injury or illness force their hand. Captain Brendon McCullum and coach Mike Hesson have expressed confidence in the four members of the New Zealand squad who haven't yet played a match at the World Cup to perform well if they have to do so.

Most other aspects of New Zealand's game are ticking along well, particularly the bowling. New Zealand has bowled out all five of its opponents to date and Sri Lanka's 233 in the opening match of the tournament is the highest score it has conceded so far.

Ronchi said that as wicketkeeper he has "the best seat in the house" to watch the New Zealand bowlers perform.

Swing bowlers Trent Boult and Tim Southee lead the wicket-taking list at the World Cup with 13 apiece while left-arm spinner Vettori is in third place with 12.

Ronchi said the Black Caps bowling lineup was the most consistent he had keep to and he felt privileged to have his current role.

"It's been awesome," he said. "Every game one particular bowlers seems to be doing well.

"It's not one guy carrying everyone so it's been awesome standing behind (the stumps) and watching everyone do what they can do and swinging the ball.

Because New Zealand has been chasing relatively low scores and because Williamson and Brendon McCullum have been batting well, Ronchi - at No 7 in the order - hasn't had many chances to bat at the tournament. He has no gripe about that.

"If I'm not batting that means we're doing well so I'm not complaining at all," he said. "I'm still hitting them in the nets and I'm more than happy to sit on my bum for as long as I need to."

Ronchi said although New Zealand has already qualified for the quarterfinals, and will finish atop Pool A, it will not relax in any way when it plays Bangladesh on Friday. Bangladesh has won the last seven one-day internationals between the teams - all on the subcontinent - and its win over England made clear it must be taken seriously.

"We're going to have to be on the money to beat them. It's international cricket," he said. "They're going to do well, even the minnow teams do well. Guys are capable of doing all kinds of things so if we're not on our game we'll get hurt. Hopefully we can go out there with the same mindset we have had so far."