Some parts of England have too many cases of swine flu to continue with current Government policy on containing the outbreak.

London and the West Midlands have sufficiently high numbers to move towards a policy of outbreak management, which will see people with swine flu clinically diagnosed rather than being confirmed by laboratory reports.

Swabbing will take place only for a small number of cases to keep track of the strength of the virus.

Doctors will also use the drug Tamiflu more selectively, targeting only those people with symptoms.

This means that anyone who has come into contact with somebody with swine flu will probably not receive the drug as a precaution.

Chief medical officer Sir Liam Donaldson stressed that many parts of the country were still in the containment phase and were treating people prophylactically.

Sir Liam said there could be "tens of thousands of cases" of swine flu each week by the autumn. The virus is more likely to thrive in the colder months.

So far 3,597 cases of swine flu have been confirmed in the UK but the true figure is thought to be higher.

Efforts to contain the outbreak to date have taken up a lot of resources but have been successful, Sir Liam said.

Sir Liam said: "We still think we are heading for the largest surge of cases in the autumn and winter.

"When you move to treatment phase, you need to time that correctly."

Health Secretary Andy Burnham urged people to continue observing good hygiene, such as washing their hands, covering their mouth when coughing and disposing of dirty tissues.

"If you have flu-like symptoms and are concerned, the advice is to stay at home," he said.

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