As a new case of the A/H1N1 flu in England is taking the confirmed total in Britain to 28, England's chief medical officer said on Tuesday that it is "too early to assume the swine flu (A/H1N1 flu) outbreak is a mild infection."

Liam Donaldson, England's chief medical officer, was quoted by BBC as warning against complacency because flu viruses could change character "very rapidly, though no-one in Britain has died.

Leaflets suggesting ways people can treat and prevent catching H1N1 flu have begun dropping through doors.

Donaldson, who updated the government's weekly cabinet meeting on the flu situation, said that "we may see an apparent peak in the incidents over the next month or so, but that doesn't mean it's gone away."

"It could be that we'll see a resurgence of the virus in the autumn and winter when the normal flu season starts," he said, adding that "These next few months are vitally important in understanding what sort of virus we're dealing with."

The latest case of H1N1 flu, confirmed on Tuesday, was an adult from the Slough area of Berkshire, less than an hour's drive to the west of London.

The individual, who is associated with travel to Mexico, is responding well to antiviral drugs, the authority added.

The new case brings the overall of confirmed cases in Britain to 28, of which 24 in England and four in Scotland.

Meanwhile, five British schools hit by the virus, were closed up and beginning rescheduling GCSEs and A-levels as the summer exam season begins.

Three of the schools are in London, with one in Devon and one in South Gloucestershire. Four are secondary schools.

More than 1,200 private schools have been given legal advice by the Independent Schools Council, which suggests setting up "quarantine rooms" for pupils suspected of having the virus.

Around 300 other people in Britain are currently awaiting the results of tests to determine whether they have the virus.