The swine flu virus has run out of steam - temporarily at least. The rampant spread of the infection across the country has slowed according to official figures showing 110,000 new cases last week, compared with 100,000 the week before.

After a month in which cases of swine flu have been doubling every seven days, Sir Liam Donaldson, the Government's Chief Medical Officer, said: "It is possible the virus has had its fill of us for the moment. We are probably seeing a downturn in the illness. It doesn't mean it won't peak again, or return in the autumn which we expect. We don't anticipate it staying away for long."

There were several trends indicating a downturn, Sir Liam said. Cases in children aged 5-14, who are starting their summer holidays, were sharply down. Consultations for flu-like illness with GPs dropped from 155 per 100,000 last week to 138 per 100,000, according to the Royal College of GPs Monitoring Unit. A separate network of over 3,300 GP practices monitored by QSurveillance showed consultations last Tuesday were less than a third of the consultations seen the previous Tuesday. But the picture is complicated by the launch of the National Flu Pandemic service last week which issued anti-viral drugs to 150,000 patients who contacted it online and over the phone. Sir Liam said many of those patients might never have contacted their GP but remained below the radar, and only appeared as flu "cases" because the National Flu Pandemic Service was easier to access. The illness appears to have peaked in some parts of London and the West Midlands but to be still rising in the North east, North West and South West.

There is no sign the virus is changing or becoming more virulent. Analysis shows 27 confirmed deaths associated with swine flu, one more than last week, and a reduction in the numbers hospitalised to 746, compared with 840 last week. However, there was an increase in the number in critical care to 81, up from 63 last week.

Asked why the infection had receded, Sir Liam said: "There's a climatic element to it. It is extremely unusual [to see flu] in summer. It is one of the mysteries of the way the flu virus behaves. But there is a strong feeling it will surge forward in the autumn."

For the first time, Sir Liam included details of the number of people affected in each age group. The cumulative totals show around 230,000 adults have been infected compared with 100,000 children under 15 - a ratio of over two adults to every child.

Earlier this week a report from the Lords' science and technology committee criticised the government's handling of swine flu. It called for clarity on how intensive and critical care departments will cope with high patient numbers.

Intensive care specialists had already warned that swine flu cases could overwhelm intensive care departments in England.

Ian Dalton, the National Director for NHS Flu Resilience, said he was working with the 10 Strategic Health Authorities to produce an updated critical care plan by the end of August.

"It will set out the action that has to be taken in order to increase critical care capacity. I would like to reassure people that this will build on a lot of previous planning," he said.

There has been a slight rise in swine flu cases in Scotland, with 4,300 cases in the past week.

Wales is also reporting a small rise in cases of flu-like illness with 4,410 in the past week and Northern Ireland saw 10 new cases.

The flu service is not covering the rest of the UK, as Wales, Northern Ireland and Scotland have all experienced much less demand.

The flu hotline number is 0800 1 513 100

Commenting on the latest pandemic plans announced today, Health Secretary Andy Burnham said: "There are early signs that the rate of increase in swine flu infections may be slowing down. This is encouraging, but there will be no let-up in our preparations. Even if the number of infections starts to fall, they may rise again, possibly much faster, as we enter the main flu season in the autumn.

"There are two key areas; critical care and vaccination strategy, where we need to finalise our plans to ensure that we are on a sound footing going into Autumn.

"On critical care, work has been ongoing within the NHS to plan for how to manage the service in the main flu season. Today, I've asked Ian Dalton, the National Director for NHS Flu Resilience, to work with the 10 Strategic Health Authorities to produce a Critical Care Plan for the NHS by the end of next month. This will draw upon the excellent work the Health Service has already done and will set out the actions they need to take to increase the number of critical care beds, ready for the autumn.

"By the end of August, we will also publish a vaccination plan that will include decisions on priority groups and the method of delivery. "We already have plans in place to cope with a second wave of swine flu. We have enough Tamiflu for everyone who needs it and we are first in line for the vaccine. The National Pandemic Flu Service is up and running and is taking pressure off GPs and NHS Direct leaving them free to deal with other patients most in need. "The NHS is doing an excellent job and I want to thank NHS staff for their hard work and dedication."