The company said it had decided to temporarily close the William Rufus in Carlisle following 24 employees who went into self-isolation.
Wetherspoon said it informed local authorities and handed over the contact details of its workers to NHS testing and tracing officials.
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The staff member, who had worked shifts on July 24 and 28, completed a home test kit on Monday and found out the result on Thursday.
The bosses decided to close the pub early on Friday.
However, Wetherspoon said contact details for patrons who have visited the pub in the past two days have yet to be requested.
“Wetherspoon has made the decision to temporarily close the pub,” spokesman Eddie Gershon said.
“The local authority did not advise the company to close the pub.
“Local authorities and public health organizations have been very helpful and supportive.
“Details of testing and tracing customers have not yet been requested by authorities but are available when needed.
“Wetherspoon will reopen the pub as and when it can secure the number of staff needed to do so safely. “