In reply to Mick Ryan - UKClimbing.com:
A number of us were struck down by this whilst on the island for a week a fortnight ago.
The "viral nature" was mentioned by staff who reassured us that a number of precautions were being taken to ensure it didn't spread further.
However, our suspicion as to how genuine this was, was aroused when they said they were putting anti-bacterial agents in the drinking water!!!