England and London Wasps are anxiously waiting news on the full extent of Paul Sackey's illness.
The flying winger was withdrawn from Wasps Heineken Cup defeat to Munster on Saturday after feeling unwell - with Sackey initially showing signs of mumps.
Sackey was immediately flown home and placed in quarantine - with the local Health Protection Agency called in to help confirm the diagnosis.
A statement from Wasps read: "Paul Sackey has undergone tests to determine the nature of the virus he has contracted.
"Sackey started to show symptoms before Saturday's Heineken Cup game against Munster, and as a result he was immediately quarantined and returned home.
"Sackey has undergone a saliva test to determine the nature of the virus, and the results of that test will be returned to the club Tuesday.
"At present, no other member of the London Wasps squad has shown any similar symptoms."
The news is another blow for England's preparations to take on Wales, with Simon Shaw and Peter Richards also a doubt.
Both players are waiting on results of MRI scans, with Wasps second row Shaw injuring his ankle and London Irish scrum-half Richards suffering damage to his tendons in his left bicep.
As a result London Irish back Paul Hodgson, Gloucester No.8 Luke Narraway and Bath flanker Michael Lipman have been called into England's training squad.

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