England's entire ODI squad has been forced to self-isolate two days before the start of their series against Pakistan following seven positive Covid-19 tests among the team's players and management.

Three players and four members of management returned positive results from a round of PCR testing in Bristol on Monday, after the third ODI against Sri Lanka. "In collaboration with Public Health England, Public Health Wales and Bristol Local Health Authority, those impacted will now observe a period of self-isolation from July 4 following the UK Government's protocol on quarantine," an ECB statement said.

"The remaining members of the party have been deemed close contacts and will also isolate."

The ECB confirmed that the limited-overs series against Pakistan will go ahead as planned, with Ben Stokes due to return to international duty ahead of schedule and captain the squad, which features nine uncapped players. Several have been pulled out of the ongoing round of County Championship fixtures to join up with the new squad and will undertake PCR tests in order to ensure the safety of the new squad.

Chris Silverwood, England's head coach who had been due to take time off during the white-ball series, will return to oversee the team. Both of Silverwood's assistants, Graham Thorpe and Paul Collingwood, were part of the group now having to self-isolate.

An ECB spokesperson confirmed that the majority of those who tested positive are asymptomatic, with those unwell not currently experiencing "significant" issues. The 10-day isolation period, backdated to July 4, means all involved are ruled out of the three Pakistan ODIs, to be held at Cardiff, Lord's and Edgbaston.

Tom Harrison, the ECB's chief executive, said: ''We have been mindful that the emergence of the Delta variant, along with our move away from the stringent enforcement of biosecure 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. We also recognise the impact this news will have on our first-class counties and their men's playing squads and thank them, along with our partners Sky and Royal London, for their ongoing support in dealing with this pandemic.''

The ECB had been keen to move away from the idea of biosecure "bubbles" this summer, amid a recognition of the toll such restrictions take on players and staff. England have a Covid compliance officer, Phil Davies, who has been advising the squad on what they are able to do in and around different venues, depending on local data.

England players are also part of the nationwide vaccination programme - Jason Roy posted on Instagram about receiving his first jab on Monday. Everyone in the group had received at least one shot of the vaccine.

There has still been a regular testing regime, which led to a number of match officials going into isolation after the T20I series against Sri Lanka as a result of a positive test for Phil Whitticase, the match referee. Concerns around biosecurity also saw Sri Lanka send home three players - Kusal Mendis, Niroshan Dickwella and Danushka Gunathilaka - after an unsanctioned trip into Durham city centre.

England's next opponents, Pakistan, have been been in managed isolation in Derby since arriving on June 25. The first ODI is due to take place in Cardiff on Thursday, with the ECB indicating there would be no changes to the schedule or ticketing arrangements. The second ODI, at Lord's on Saturday, is in line to be at full capacity as part of a government pilot.

The PCB released a statement saying it had been in close contact with the ECB over "concerns about the health and safety of its players" after being informed of developments on Monday evening.

"The PCB is satisfied by the assurances and guarantees provided by the ECB on behalf of its medical panel, and feels comfortable with the existing protocols that have been put in place to ensure all the Pakistan players and player support staff remain safe and secure throughout the duration of the series," the board said.

"The PCB has also been in touch with its team management and has advised them to exercise extra caution while in the hotel or at the match venue."