Eoin Morgan and Joe Root were part of England's original squadEngland will name a new squad for their ODI series with Pakistan after three players and four staff members tested positive for Covid-19.
The team were due to begin the series with an ODI in Cardiff on Thursday.
But tests administered on Monday returned seven positive results and the rest of England's party will be required to self isolate as a result.
The ECB said Ben Stokes will return to captain a squad which will be named in the next few hours.
Stokes has been absent from England duty after sustaining a broken finger when playing in the IPL earlier this year.
Chris Silverwood will also return to coach the new squad. He had been sitting out the Pakistan games to take a break before next month's Test series against India.
An ECB statement said those impacted by the positive tests "will now observe a period of self-isolation from 4 July following the UK Government's protocol on quarantine.
"The remaining members of the party have been deemed close contacts and will also isolate."
ECB chief executive officer Tom Harrison added: "We have been mindful that the emergence of the Delta variant, along with our move away from the stringent enforcement of bio secure environments, could increase the chances of an outbreak.
"We made a strategic choice to try to adapt protocols, in order to support the overall wellbeing of our players and management staff who have spent much of the last 14 months living in very restricted conditions.
"Overnight we have worked swiftly to identify a new squad, and we are grateful to Ben Stokes who will return to England duties to captain."
The 10-day isolation period the squad will face will will span all three ODIs against Pakistan.
Thursday's fixture at Sophia Gardens is followed by games at Lord's on 10 July and Edgbaston three days later.
England then face three Twenty20 fixtures against Pakistan on 16, 18 and 20 July.
'A chaotic situation'
BBC Sport cricket correspondent Jonathan Agnew
Ben Stokes has only just come back to cricket himself. He has played a few games for Durham and is inching himself back.
Clearly it's a pretty chaotic situation.
It will be a great chance for some and England had a big squad anyway for cover, including coronavirus.
Fortunately from England's point of view this is not the highest-profile series they are in. The Twenty20 series is important and there are not many games left for that team to get organised for the World Cup.
The 50-overs stuff that starts is not so important but there will be a real disappointment amongst the England camp if these players then do miss the Twenty20 series.
