A previously healthy man has died in hospital after contracting swine flu, bringing the total number of deaths in Britain linked to the virus to 15.

The patient, from Essex, is the first person without an underlying health condition to die from swine flu complications. NHS East of England confirmed that the man had died at Basildon and Thurrock University Hospitals NHS Foundation Trust. The patient’s family did not want further details to be released last night.

Regional health officials said: “This case tragically underlines that, although the virus is generally mild in most people, it is more severe in some cases. As with all flu-like viruses, some people are at higher risk than others. People who are otherwise healthy could become seriously ill or die.”

Sir Liam Donaldson, the Government’s Chief Medical Officer, said that until yesterday all the patients who had died had other health problems, but their exact medical details or whether an H1N1 infection contributed to the deaths is not known in some cases.

At least 43 people were said to be in “critical care” yesterday after becoming infected, and 335 were being treated in hospital.

John Oxford, Professor of Virology at Queen Mary’s College of Medicine in London, said that the man’s death did not give any extra cause for concern. “We have all been gritting our teeth, waiting for this to happen. This doesn’t necessarily mean the virus has mutated,” he said.

“Whether more patients with no underlying health problems die of the disease really depends on what the virus does next.”

People with suspected swine flu could be allowed to take up to two weeks off work without a doctor’s note, under plans for dealing with the pandemic being discussed by the Government. Employees are at present allowed to sign themselves off sick for up to seven days.

Rates of illness are already approaching epidemic levels in London and the West Midlands, and doctors say that several million people could become ill with the onset of seasonal flu in the autumn and winter.

The proposals to extend sick leave, reported in Personnel Today magazine, would stay in place for six months in an effort to contain the spread of the virus. However, business leaders fear that workers could abuse the system and see the changes as a “freedom pass” to taking time off.

Previous estimates suggest that widespread H1N1 infections could cost employers £1.5 billion a day as up to a quarter of the workforce take time off.

At least 27,000 people contacted their GP to complain of “flu-like illness” last week, but laboratory reports suggest that only 28 per cent of those, about 8,000 people, had the swine flu virus.

Those with symptoms such as a high temperature, dry cough and general feeling of weariness are encouraged to stay at home and contact health services by phone.

Professor Sayeed Khan, chief medical adviser at the manufacturers’ body EEF, said: “The advice is not to visit your GP if you get swine flu. Being realistic, there will be some people who think, ‘I’ve got a bit of a cold’ and will stay off work. There’s nothing you can do to fix that.”

The Department for Work and Pensions said: “We don’t want people to feel obliged to leave the home or return to work when they are still unwell or put an unnecessary burden on GPs in a pandemic. Contingency plans therefore include the possibility of extending self-certification to 14 days for a limited period.”

Employers’ groups admitted that short-term measures to contain swine flu were likely to be necessary. Neil Carberry, head of employment policy at the CBI, said: “The CBI has had a number of discussions with the Department of Health about this. Employers need to be thinking through their business resilience plans in the face of the threat of a pandemic.”

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