Chelsea striker Daniel Sturridge is undergoing tests for suspected meningitis, according to reports here on Tuesday.
The 22-year-old fell ill over the weekend and was admitted to St Mary's hospital in Paddington for tests, the Press Association reported.
Doctors reportedly suspect Sturridge may be suffering from the viral strain of the disease, whose symptoms are generally mild and which can be overcome without the need for medical treatment.
Although his condition is said to have improved over the last 48 hours, his place in the 23-man Great Britain football squad, named on Monday, is now in doubt.
Stuart Pearce's squad will meet at the Team GB holding camp in Loughborough next weekend, and Football Association (FA) medical staff will assess the results of tests before deciding if Sturridge can still play a part.
Pearce has until July 25 to select a replacement should Sturridge be forced to withdraw.