A swine flu sufferer has died in London, health officials have announced.

The fourth person to die in the UK is understood to have been a 19-year-old man from south London who had serious underlying health problems.

He died on Wednesday and tests afterwards found he had the virus.

His was announced a day after it was revealed that the number of new cases could reach 100,000 per day by the end of next month.

Chief Medical Officer Sir Liam Donaldson, who confirmed on Thursday that the UK has moved past the stage of containing the swine flu outbreak and into the "treatment phase", said there was no need for people to resort to the internet to self-medicate amid fears over the spread.

He said Britain had a massive stockpile of Tamiflu and would be one of the first countries to have access to a vaccine, with the first supplies arriving at the end of August.

Sir Liam said: "There's generally a growth in people ordering drugs from the internet worldwide and there's a lot of concern amongst health authorities that people might buy counterfeit drugs.

"I think this is a similar situation - people shouldn't buy Tamiflu from the internet. We have got a massive stockpile in this country and everybody can have access to it through the National Health Service."

Sir Liam added he was "surprised" health services had controlled the virus for as long as they had. The first case in Britain was recorded in April.

He said: "We have been dealing with it very aggressively so far - we have investigated every case, we've treated their contacts, we've closed schools and all of that has helped slow the spread.

"We are surprised we have been able to run it as long as we have like this. Flu viruses spread extremely quickly so this is very much going as expected."

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