Roy Hodgson on alert as virus sweeps through England camp ahead of Ukraine match

Roy Hodgson will discover this morning whether a virus in the England squad has ruled out any more of his players for tonight's World Cup qualifier against Ukraine after illness suffered by Theo Walcott and Daniel Sturridge forced him into three emergency call-ups yesterday.

Raheem Sterling, the 17-year-old from Liverpool who has played just 210 minutes of Premier League football was the surprise choice, along with Southampton's uncapped Adam Lallana. The Spurs midfielder Jake Livermore, who made his England debut against Italy last month, was also called into the squad.

Walcott was sent back to Arsenal yesterday after he woke up "violently ill", Hodgson said. Sturridge also missed training with stomach cramps, leaving the England manager with just 16 outfield players from the 21 picked in the original squad for his session at Arsenal's London Colney training ground. It is hoped that the two players' illnesses are not related but, as a precaution, Sturridge was placed in isolation from the rest of the squad.

As has been England's approach to all home games in recent years, the squad have been staying at The Grove in Hertfordshire, although they will move to the custom-built St George's Park in Staffordshire next month.

After initial consideration of delaying Sterling, Lallana and Livermore's arrival at the hotel until this morning because of the suspected virus, it was agreed that the three should come yesterday. Hodgson has said that all of them should not expect to be involved in the game unless events take a dramatic turn for the worse.

Hodgson said that he hoped the virus was not going round his squad. "That is one of the reasons we were quite anxious to get Theo back home as soon as possible and we've kept Daniel away from the other players," he said. "We've called up some extra players just in case, because you never know, you could wake up [this] morning and one or two are suffering. We hope it is just an isolated case."

Brendan Rodgers, the Liverpool manager, said last week that he was glad that Sterling had been selected for England Under-19s instead of the Under-21s so that he was not exposed to too much expectation. However, the teenager, who was born in Jamaica but went to school in Wembley, has now leapfrogged the Under-21s and will travel to the game having not even trained with the England squad.

Hodgson said that he had spoken to Rodgers to clear up any issues over the selection of Sterling. "He [Rodgers] is satisfied," Hodgson said. "I've explained the thinking behind him [Sterling] coming in, and I'll make it clear to Raheem. He'll be pretty lucky to get close to the field because there were plenty of players who were chosen in front of him.

"I can only hope he takes it in the right way, and that it's great to be invited into the England set-up. He mustn't think he's become a part of the set-up and has made it. He has to try, next time, to make sure he is one of the original 23. We'll be watching him before October to see whether he'll merit a place in the squad."

Hodgson dismissed suggestions that the FA was trying to shore up Sterling's future following interest in him from Jamaica. "That's not why I've called him up," he said. "I'm prouder of the English football shirt than that. If Raheem decides he wants to play for Jamaica, he'll go with my blessing. But I'd like to think he'll have the right desire to play for England."

There are now 12 players missing through injury and illness who would nominally have been in the England squad had they been fit. Walcott's withdrawal takes to five the number of players who have pulled out since the squad was named on Thursday.