Legspinner Shadab Khan was left tense and frustrated after learning that he was suffering from hepatitis, two days after being picked for the Pakistan squads for the tour of England and the World Cup.

A blood test had revealed Shadab was suffering from hepatitis, and was subsequently replaced by Yasir Shah in the squad for the England series, while the PCB arranged an appointment with a London-based gastroenterology and hepatology specialist. While Shadab recovered from the viral infection over the last month, his health was still a concern, with his chances of playing the World Cup at risk. But now he has been declared fit and is set to join the squad after the England series.

"When you suddenly get to know that you have a viral [infection] in your blood, naturally I got frustrated but my team-mates and friends have been very supportive," Shadab said. "I have a strong belief that whatever happens, happens for a reason and for good. I was tensed up on the first day but then I told my friends that whatever happened was in the past. If anything good is to happen, it will happen. So I asked them to avoid talking to me about it."

Shadab was given a two-week course of medication and was prescribed complete rest. He was declared fit after undergoing another round of blood tests in Lahore earlier this week and is set to leave for England soon.

"I was always hopeful because the viral infection was found at its initial stage," Shadab said. "With two weeks of medication, it's out of my blood. Now I am heading to the World Cup. We [Pakistan] have been going there [to England] regularly over the last three years so it isn't really difficult to acclimatise. All I have to do is to get in my rhythm otherwise I am mentally prepared for the challenge."

Shadab has been Pakistan's key strike bowler in the middle overs for the last two years, and his return is a boost for the side. His replacement, Yasir, hasn't made an impact as Pakistan have struggled with their bowling in the ongoing ODI series against England. Yasir's ODI form has been a far cry from the quality that has marked him out as an elite Test bowler, and he was left out of the third ODI against England on Tuesday after conceding 60 runs in seven overs during the second ODI in Southampton last week.

Pakistan have taken only seven England wickets in the last two ODIs, after the first match was washed out. The hosts scored 373 in the second ODI and on Tuesday, chased down 359 with 31 balls and six wickets to spare. Shadab who has a knack of picking wickets in the middle overs, believes the Pakistan bowlers are not in rhythm.

"Nowadays you have to take wickets because cricket has become very fast and even 350 isn't a par score," Shadab said, reflecting on Pakistan's performance in England so far. "Yes we have been struggling with the ball in the middle overs, but the way the batting is performing is a good sign. No doubt we lost the games but we put up a good fight and played competitive cricket, which gives a lot of boost to the team. Pakistan, anyway, still have the ability to win the remaining games.

"I have already played in a competitive tournament, in the 2017 Champions Trophy, which we won. Victory indeed has its own taste. Even though we lost a few games, I know how to adapt in a big tournament. Our team has 100% skills to do well in the World Cup. Yes, they are struggling but so are the other teams in many ways. They are playing good cricket overall. Yes, the bowlers are not doing well, they are actually not in the rhythm required but once they start clicking, we will start winning the games. Overall, when you are missing four key players [Shadab, Mohammad Amir, Mohammad Hafeez, Shoaib Malik] it becomes increasingly tough. But there is a difference between pressure for a series and the World Cup, so I am optimistic about our chances there and we will try to win the World Cup."