Officials say swine flu cases in England increased by 56 per cent last week.

That is based on the Britain Health Protection Agency's estimates that there were 39,000 to 169,000 news cases last week, compared with 27,000 to 115,000 the week before that.

The estimates, based on statistics such as doctor visits and calls to the nation's swine flu hot line, have a wide margin of error.

The agency said on Thursday that swine flu was mainly hitting children under 14. The largest increase in Tamiflu distribution was to children aged 1 to 4.

Unlike most countries, Britain gives out Tamiflu via call centre workers with no medical training.

Britain started its swine flu vaccination program last week for health workers and people with underlying medical problems first.