Arrowe Park Hospital in Wirral has confirmed that a second office worker has tested positive for swine flu.
The first confirmed case made a complete recovery and was cleared to return to work on 15 June.
The second patient was already off work with symptoms when the first patient returned to work and is currently making a good recovery at home.
Neither of the two office workers had been in contact with patients, a Health Protection Agency statement said.
Close contacts have been treated and no further action is necessary in their workplace, it added.
"The majority of swine flu cases in the UK and indeed around the world have had mild illness," the statement said.
"There have been few examples of swine flu cases circulating in a workplace and no evidence to date of transmission in the workplace in the North West region."