Haider Ali, Shadab Khan and Haris Rauf have tested positive for Covid-19, the PCB have announced.

The three players, who, according to the board, are all asymptomatic, will now undergo a period of isolation. Imad Wasim and Usman Shinwari were the other players tested in Rawalpindi alongside the trio, with their results coming back as negative. The rest of the players and officials, barring bowling coach Waqar Younis, Shoaib Malik and Cliffe Deacon, all underwent tests, with their results expected back on Tuesday.

The developments lay bare the stark challenges of going ahead with international cricket in these times, with Pakistan's departure for England for a three-Test three-T20I tour less than a week away.

The team is due to arrive in the UK five weeks before the start of the series in August, with the travelling party self-containing in a "bubble" which means they will not contact anyone outside their group. Families are to be prohibited from joining the players, and just last week, Haris Sohail and Mohammad Amir announced they would not take part.

As yet, the entire squad has not been required to go into self-isolation because the team hasn't begun training collectively, but the PCB did advise anyone who had been in contact with the trio to "self-isolate immediately".

According to the protocols laid out by the PCB for the England tour, it is not impossible that the trio may still be able to join the tour at a later date, even though they will not now be permitted to travel with the main squad, which is due to leave for Manchester from Lahore on a specially chartered flight on June 28.

Provided the trio recover after 14 days in isolation and test negative thereafter, they will then be allowed to take a commercial flight to England, where they will be admitted into the bubble that the existing players are in, after following the UK government's guidelines. All players will be tested again when they land in England.

While these are the first three players to test positive from what is expected to be the travelling group, it is not the first time the pandemic has affected Pakistan's preparations for the tour of England.

A fortnight ago, the PCB scrapped plans to host a training camp in Pakistan ahead of the tour, with the rapid growth of cases in the country making it impossible to achieve a bio-secure environment. That necessitated bringing forward the team's departure to England, with the aim of conducting a camp there, where the virus has passed its peak.

Pakistan has seen a surge of Covid-19 cases over the past few weeks, prompting the government to reimpose a partial lockdown earlier this week. The country currently has around 185,000 confirmed cases, which ranks it 13th globally, while it is believed the pandemic has not yet reached its peak in the country.

Last week, former Pakistan captain Shahid Afridi announced he had tested positive for the virus, and was self-isolating. Taufeeq Umar also contracted the virus, going on to make a full recovery.

Speaking prior to the squad's departure, Dr Sohail Saleem, Pakistan Cricket Board's (PCB's) director of sports medicine, conceded that the players were taking a "big risk" embarking on the tour of England in the midst of a pandemic.

"We are trying to build a new normal, redefining etiquette - respiratory marks, hand washing," Dr Saleem said. "It is a combination of many thing to make sure that we are keeping safe or reducing the risk factor to the minimum.

Danyal Rasool is a sub-editor at ESPNcricinfo. @Danny61000