More than 6,200 people worldwide have died from swine flu, the WHO said

The Government's most senior medical adviser has warned that the swine flu pandemic was placing NHS hospitals under a "lot of pressure" in coping with the most seriously ill patients.

Chief medical officer Sir Liam Donaldson said the shortage of intensive care beds was a "concern" at a time when more people are being hit with severe symptoms.

But he said he hoped the vaccination programme would help contain the spread of the virus.

He told the number of people affected by swine flu had increased at a slower rate than feared.

"But what we are seeing is that while most people generally get a mild illness, a small proportion of people are getting very serious illnesses.

"It's taking them into hospital and a small proportion are dying.

"The good thing about the situation at the moment is we are getting a bit of breathing space with the relatively slow increase in cases to be able to get the vaccine in place."

Asked about the strain the pandemic was placing on the NHS he said: "We are seeing the general practitioner services not under a great deal of pressure at the moment and we also have this alternative route of access through the internet and the telephone lines to let people get assessed and get anti-virals.

"So that side of things is looking good but on the hospital side the intensive care beds are under a lot of pressure.

"We have plans to expand them but that is a concern at the moment - the serious end of the spectrum, the hospitalised patients."