Officials at Coventry's University Hospital have expressed surprise over the increased numbers of people at accident and emergency.
Up to 500 people a day at times have visited the facility over three weeks compared to an average of 450.
University Hospitals Coventry and Warwickshire NHS Trust said it was surprised by the high sickness level.
The trust appealed for "a few moments of extra thought" by people about whether they need to go to casualty.
It added there was not "anything obvious" and there has not been a cold snap or any snow around.
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