Swine flu cases double in a weekThe estimated number of new swine flu cases has almost doubled in the last seven days.
The overall number of deaths in the UK has risen to 128, with 93 deaths recorded in England, 21 in Scotland, eight in Northern Ireland and six in Wales.
But Chief Medical Officer Sir Liam Donaldson said he was most worried by the number of hospital cases, which have risen in England to 506, with 99 in critical care.
The number in critical care is the highest since the pandemic began.
Sir Liam said: "We don't understand why this has happened. It looks as if the virus is having a different impact in the flu season than it had in the summer."
He said he was concerned by the high proportion of deaths in younger age groups, describing it as a "very unusual pattern for flu".
More than half (54 per cent) of H1N1 deaths have been in the under-45 age group, in contrast with normal seasonal flu which is more dangerous for the over-65s.
One in three deaths related to people who had little or no underlying health problems.
ITN