Swine flu case in Clevedon
Others workers at the office in Tickenham Road, which employs around 540 people, are also understood to have flu-like symptoms.
All staff were informed of the case yesterday afternoon, but told to keep coming into work.
Tissues were being issued to staff to help stop the spread of infection and a clean-up of all surfaces, including the plants and revolving glass doors in reception, was being carried out.
Official confirmation of the case has not been made because the routine use of swabs that are then tested for the presence of the virus has been stopped.
Karen Daniels, from NHS North Somerset, said: "We are continuing to advise people, bin it and kill it by making sure tissues are disposed of and hands are washed thoroughly.
"If you feel unwell, contact your GP who will give advice."
Clerical Medical media relations manager Richard Janes said: "We take the health and safety of our colleagues and customers extremely seriously and have a range of measures in place that reflect this."
Swine Flu symptoms resemble regular flu infection and include fever, fatigue, lack of appetite, coughing and sore throat.
Some people with swine flu have also reported vomiting and diarrhoea.
Testing has shown that the human swine influenza H1N1 can be treated with the antivirals oseltamavir (Tamiflu) and zanamivir (Relenza).
Most of the previously reported swine influenza cases recovered fully from the disease without requiring medical attention and without antiviral medicines.
General infection control practices can help to reduce transmission of all viruses.
This includes covering the nose and mouth when coughing or sneezing, using a tissue when possible and disposing of dirty tissues promptly and carefully.
Good basic hygiene should always be maintained such as washing hands with soap and water to reduce the spread of the virus.
Anyone who believes they may have swine flu should contact their GP surgery, NHS Direct on 0845 46 47 or the Department of Health helpline 0800 1513513.
Comment on this story