Joe Root, the England captain, was admitted to hospital in Sydney, suffering from severe dehydration, amid doubts as to whether he would be fit to resume his rearguard in the fifth and final Test at the SCG.

Root, who batted for three hours to reach the close of the fourth day's play on 42 not out, had been in the field for all but six overs of the hottest day on record for a Test match in Australia. Temperatures in some parts of Sydney reached 47.3C, the highest in the city for 79 years.

Root succumbed to bouts of diarrhoea and vomiting overnight, and did not arrive at the ground until after the start of play. It was later announced by the ECB that Root was suffering from a viral gastroenteritis bug, rather than the effects of heat exhaustion.

England are already 3-0 down in the series and were precariously placed on 93 for 4 overnight, needing another 210 runs to make Australia bat again. Moeen Ali took the field alongside Jonny Bairstow but Root was fit enough to resume his innings after Moeen's dismissal on the hour mark, and soon moved to his fifty.

Before it was made clear that Root was affected by a virus, there had been speculation about the damaging effects of playing in high temperatures. Dean Jones, the former Australia batsman who famously ended up on a drip after making 210 in oppressive heat during the tied Test in Madras in 1986, stated on Twitter that the sport needs to take the issue of exposure to extreme conditions more seriously.

"After speaking to a couple of doctors this morning.. in my opinion cricket should be called off after 41C," Jones wrote. "It's a workplace issue now.. just my opinion."