Sam Curran is self-isolating in his room at the Ageas Bowl after feeling sick on Wednesday night.
Curran made an unbeaten 15 on the first evening of England's intra-squad warm-up match, but took no part in the game after suffering from "sickness and diarrhoea overnight", according to an ECB statement.
The statement added that Curran was feeling better on Thursday afternoon, but confirmed that he would play no further part in the ongoing warm-up match. He has been monitored by the team doctor, Mark Wotherspoon, who was wearing full PPE during the assessment, and was tested for Covid-19 during the lunch interval.
The news will come as a concern for England so close to the first Test. There is no suggestion, at this stage, that Curran has come into contact with the virus, especially within the bio-secure arrangements at the Ageas Bowl, which make it one of the most low-risk environments in the country.
However, his illness will undoubtedly be a source of frustration given that he has been unable to bowl in this warm-up match after going so long without competitive cricket. Indeed, it is now difficult to see how will play next week, not least with so many other seamers in contention.
The results of Curran's Covid-19 test are expected back on Friday, although the protocols in the event of a positive result are not at this stage being divulged by the ECB. However, he would be likely to go into a seven-day self-isolation - it is unclear whether that would take place within the team bubble or at home - and Public Health England would also be notified.
The remainder of the England players and management are due to be tested again for Covid on Sunday. At this stage, that testing date is unlikely to be brought forward. An ECB spokesperson confirmed that the West Indies camp and other stakeholders within the team environment had been notified.
Amar Virdi, the offspinner, was a late addition to Team Buttler - although he was officially replacing Jofra Archer, who experienced soreness from new bowling boots - having initially missed out on the squad. He came on to bowl shortly before the close on the second day and took the final wicket to fall.
The ECB is expected to issue a formal update on Olly Stone's availability on Friday. Stone has played no part in the warm-up match due to a niggle in his left hamstring.
Matt Roller is an assistant editor at ESPNcricinfo. He tweets at @mroller98